docs: refresh README and 1.6.0 release notes

README:
- The InfluxDB/Prometheus metric backends described in the overview do not
  exist; describe the built-in metric store and the external cc-metric-store
  routing instead.
- The demo instructions still told the reader to add cluster entries to
  config.json. Clusters come from the cluster.json in each job archive
  directory.
- Dead link to docs/JWT-Handling.md (there is no docs/ directory), configs/
  described as holding environment-variable documentation, missing tools, OIDC
  missing from the list of authentication methods, and web/ indented as a child
  of tools/ in the project structure.
- Added a Configuration section: the top-level sections and which are required,
  the "-file" indirection, and how unknown keys are handled per section.

ReleaseNotes: the 1.6.0 entry covered only the session backend and none of the
breaking changes. Added the .env removal, the policy-based resampling config
(configs carrying trigger/resolutions/minimum-points now abort), the switch to
average downsampling, the OIDC role-mapping requirement, LDAP role-filters, the
auth schema now actually validating, and the new features and bug fixes since
v1.5.4. Fixed the clusterockpit.org typo and marked the 1.5.2 known-issues list
as belonging to that release.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

README.md

@@ -30,10 +30,12 @@ based on a GraphQL API. The web frontend is also served by the backend using
 [Bootstrap Icons](https://icons.getbootstrap.com/).
 
 The backend uses [SQLite 3](https://sqlite.org/) as the relational SQL database.
-While there are metric data backends for the InfluxDB and Prometheus time series
+Time-series metric data is kept separately: cc-backend ships with a built-in
-databases, the only tested and supported setup is to use cc-metric-store as the
+in-memory metric store (configured via the `metric-store` section) that persists
-metric data backend. Documentation on how to integrate ClusterCockpit with other
+its buffers with a write-ahead log and periodic binary checkpoints. Alternatively
-time series databases will be added in the future.
+(or in addition, routed per cluster) it can query one or more external
+[cc-metric-store](https://github.com/ClusterCockpit/cc-metric-store) instances via
+the `metric-store-external` section. At least one of the two must be configured.
 
 For real-time integration with HPC systems, the backend can subscribe to
 [NATS](https://nats.io/) subjects to receive job start/stop events and node
@@ -42,8 +44,9 @@ state updates, providing an alternative to REST API polling.
 Completed batch jobs are stored in a file-based job archive according to
 [this specification](https://github.com/ClusterCockpit/cc-specifications/tree/main/job-archive).
 The backend supports authentication via local accounts, an external LDAP
-directory, and JWT tokens. Authorization for APIs is implemented with
+directory, an OpenID Connect provider, and JWT tokens. Authorization for APIs is
-[JWT](https://jwt.io/) tokens created with public/private key encryption.
+implemented with [JWT](https://jwt.io/) tokens created with public/private key
+encryption.
 
 You find a detailed documentation on the [ClusterCockpit
 Webpage](https://clustercockpit.org).
@@ -77,13 +80,16 @@ Execute the following steps:
 
 ```shell
 ./cc-backend -init
-vim config.json (Add a second cluster entry and name the clusters alex and fritz)
 wget https://hpc-mover.rrze.uni-erlangen.de/HPC-Data/0x7b58aefb/eig7ahyo6fo2bais0ephuf2aitohv1ai/job-archive-demo.tar
 tar xf job-archive-demo.tar
 ./cc-backend -init-db -add-user demo:admin:demo -loglevel info
 ./cc-backend -server -dev -loglevel info
 ```
 
+The clusters are read from the job archive (one directory with a `cluster.json`
+per cluster), so no cluster list has to be maintained in `config.json`. The demo
+archive contains the clusters `alex` and `fritz`.
+
 You can access the web interface at [http://localhost:8080](http://localhost:8080).
 Credentials for login are `demo:demo`.
 Please note that some views do not work without a metric backend (e.g., the
@@ -130,6 +136,8 @@ cd ./cc-backend/
 make
 
 cp configs/config.json .
+# config.json references the UI defaults via "ui-file", so copy that too:
+cp configs/uiConfig.json .
 # EDIT config.json BEFORE YOU DEPLOY: change the secrets under "auth.jwts"
 # ("public-key"/"private-key"). Each secret can also be supplied via an
 # environment variable (e.g. JWT_PUBLIC_KEY), which takes precedence over the
@@ -172,6 +180,42 @@ For production deployments, serve cc-backend over HTTPS so the session cookie is
 marked `Secure`. If you terminate TLS at a reverse proxy, prefer letting
 cc-backend serve HTTPS directly for now so the flag is applied.
 
+## Configuration
+
+cc-backend reads a single JSON configuration file (`./config.json` by default,
+override with `-config`). Every top-level key is one configuration section:
+
+| Section                 | Required | Description                                                                                                       |
+| ----------------------- | -------- | ----------------------------------------------------------------------------------------------------------------- |
+| `main`                  | yes      | Server address, TLS, database path and tuning, resampling defaults, footer links, job taggers, retention of node states, NATS API subjects. |
+| `auth`                  | no       | Local, LDAP, OIDC and JWT authentication including all secrets.                                                    |
+| `nats`                  | no       | Connection to the NATS broker (address, credentials). Required for the NATS API and for NATS metric ingestion.     |
+| `archive`               | no       | Job archive backend (`file`, `s3` or `sqlite`), plus archive retention and compression. Defaults to `./var/job-archive`. |
+| `metric-store`          | no*      | Built-in in-memory metric store: retention, memory cap, checkpointing, cleanup and NATS subscriptions.             |
+| `metric-store-external` | no*      | List of external cc-metric-store endpoints with a `scope` (cluster name or `*`) used to route queries.             |
+| `cron`                  | no       | Intervals of the background workers (commit-job, duration, footprint).                                             |
+| `ui`                    | no       | Defaults for the web frontend shown to new users (job list, job view, metric selections, plot options).            |
+
+\* At least one of `metric-store` and `metric-store-external` must be present,
+otherwise the server refuses to start.
+
+Any section can be moved into its own file by appending `-file` to the key and
+giving a path instead of an object, e.g. `"ui-file": "uiConfig.json"` loads the
+`ui` section from `uiConfig.json`. Unknown top-level keys are ignored with a
+warning. Unknown keys *inside* a section are always rejected by the parser: for
+`main` and `metric-store` this aborts startup, for the other sections it is
+logged as an error and the section is applied only up to the offending key — so
+watch the log after a configuration change.
+
+Annotated examples are in [`configs/`](https://github.com/ClusterCockpit/cc-backend/tree/main/configs):
+`config.json` (full featured, S3 archive, external metric stores),
+`config-large.json` (large installation with LDAP/OIDC and DB tuning),
+`config-demo.json` (minimal) and `uiConfig.json`.
+
+Cluster topology and metric definitions are **not** part of `config.json`. They
+are read from the `cluster.json` file inside each cluster's job archive
+directory; `configs/cluster.json` is a documented example.
+
 ## Database Configuration
 
 cc-backend uses SQLite as its database. For large installations, SQLite memory
@@ -272,8 +316,9 @@ The effective configuration is logged at startup for verification.
 - [`cmd/cc-backend`](https://github.com/ClusterCockpit/cc-backend/tree/main/cmd/cc-backend)
   contains the main application entry point and CLI implementation.
 - [`configs/`](https://github.com/ClusterCockpit/cc-backend/tree/main/configs)
-  contains documentation about configuration and command line options and required
+  contains sample configuration files (`config.json`, `config-demo.json`,
-  environment variables. Sample configuration files are provided.
+  `config-large.json`, `uiConfig.json`, `cluster.json`), example REST API
+  payloads, and the example rule sets for the job taggers.
 - [`init/`](https://github.com/ClusterCockpit/cc-backend/tree/main/init)
   contains an example of setting up systemd for production use.
 - [`internal/`](https://github.com/ClusterCockpit/cc-backend/tree/main/internal)
@@ -318,10 +363,14 @@ The effective configuration is logged at startup for verification.
   - [`convert-pem-pubkey`](https://github.com/ClusterCockpit/cc-backend/tree/main/tools/convert-pem-pubkey)
     Tool to convert external pubkey for use in `cc-backend`.
   - [`gen-keypair`](https://github.com/ClusterCockpit/cc-backend/tree/main/tools/gen-keypair)
-    contains a small application to generate a compatible JWT keypair. You find
+    contains a small application to generate a compatible Ed25519 JWT keypair for
-    documentation on how to use it
+    the `auth.jwts` configuration.
-    [here](https://github.com/ClusterCockpit/cc-backend/blob/main/docs/JWT-Handling.md).
+  - [`binaryCheckpointReader`](https://github.com/ClusterCockpit/cc-backend/tree/main/tools/binaryCheckpointReader)
-  - [`web/`](https://github.com/ClusterCockpit/cc-backend/tree/main/web)
+    Dumps the contents of a metric store binary checkpoint file for inspection.
+  - `dataGenerator.sh` and `grepCCLog.pl`
+    Helper scripts to generate metric line protocol test data and to filter
+    cc-backend log output.
+- [`web/`](https://github.com/ClusterCockpit/cc-backend/tree/main/web)
   Server-side templates and frontend-related files:
   - [`frontend`](https://github.com/ClusterCockpit/cc-backend/tree/main/web/frontend)
     Svelte components and static assets for the frontend UI

ReleaseNotes.md

@@ -6,9 +6,20 @@ This release replaces the browser session implementation and requires a database
 migration to version 12. Run `./cc-backend -migrate-db` after upgrading; the new
 `sessions` table is created automatically (a fresh `-init-db` also creates it).
 Existing login sessions are invalidated by the upgrade, so users have to log in
-again once. See the behavior changes below regarding the session cookie `Secure`
+again once.
-flag and the removal of the `SESSION_KEY` environment variable.
+
-For release specific notes visit the [ClusterCockpit Documentation](https://clusterockpit.org/docs/release/).
+**Two configuration changes are mandatory before starting 1.6.0:**
+
+- The `.env` file is gone. Move every secret into the `auth` section of
+  `config.json` (or export the corresponding environment variable).
+- The `main.resampling` section no longer accepts `trigger`, `resolutions` and
+  `minimum-points`. cc-backend rejects unknown keys inside `main` and aborts on
+  startup if they are still present. Replace them with `default-policy` and
+  `default-algo`.
+
+See the behavior changes below for the details, as well as for the session
+cookie `Secure` flag and the removal of the `SESSION_KEY` environment variable.
+For release specific notes visit the [ClusterCockpit Documentation](https://clustercockpit.org/docs/release/).
 
 ## Changes in 1.6.0
 
@@ -28,14 +39,117 @@ For release specific notes visit the [ClusterCockpit Documentation](https://clus
   terminate TLS at a reverse proxy and want the `Secure` flag should serve
   cc-backend over HTTPS directly for now.
 - **`SESSION_KEY` removed**: The `SESSION_KEY` environment variable is no longer
-  used and should be removed from your `.env`. Server-side sessions use random
+  used and can be dropped from your environment. Server-side sessions use random
   tokens, so no cookie-signing secret is required. It is ignored if left in place.
+- **`.env` support removed (breaking)**: The `godotenv` bootstrap, the `.env`
+  file and `configs/env-template.txt` are gone. Secrets (JWT public/private key,
+  LDAP sync password, OIDC client id/secret, cross-login keys) now live in
+  `config.json` under `auth` next to the option that uses them. Each secret can
+  still be supplied through its existing environment variable
+  (`JWT_PUBLIC_KEY`, `JWT_PRIVATE_KEY`, `LDAP_ADMIN_PASSWORD`, `OID_CLIENT_ID`,
+  `OID_CLIENT_SECRET`, `CROSS_LOGIN_JWT_PUBLIC_KEY`, `CROSS_LOGIN_JWT_HS512_KEY`),
+  which takes precedence over the config value. `-init` now writes the demo JWT
+  keys into `config.json`.
+- **Resampling configuration replaced by policies (breaking)**: The explicit
+  `trigger`, `resolutions` and `minimum-points` keys under `main.resampling` are
+  removed; `main` rejects unknown keys, so a config still carrying them aborts
+  startup. Configure `default-policy` (`low` ≈ 200, `medium` ≈ 500, `high` ≈ 1000
+  target points) and `default-algo` instead. Both are also exposed as per-user
+  settings, and the policy is now the single source for the requested resolution
+  and for the resampler's minimum-points threshold.
+- **Default downsampling algorithm is now `average`**: Previously an unset
+  algorithm fell through to cc-lib's LTTB. Average consolidation makes every
+  plotted point the true arithmetic mean of its interval; LTTB deliberately keeps
+  extremes and cannot be read as interval means. Set
+  `main.resampling.default-algo` to `lttb` to restore the old behavior.
+- **OIDC roles require an explicit mapping (breaking for role-based setups)**:
+  The hardcoded translation of token roles (which only recognised the literal
+  names `user`/`admin`/`manager`/`support` and silently dropped `api`) is
+  replaced by `auth.oidc.role-mapping`. The mapping is the sole source of roles:
+  unmapped token roles are ignored and users without a mapped role get the base
+  `user` role. Deployments whose IdP emits literal CC role names must now map
+  them explicitly (e.g. `"admin": "admin"`). Mapping targets are validated at
+  startup.
+- **LDAP can assign elevated roles**: The new optional `auth.ldap.role-filters`
+  map (role → LDAP filter) grants `admin`/`support`/`api`/`manager` to accounts
+  matching a filter. LDAP is authoritative for the roles listed there — sync and
+  login both add *and remove* them to match group membership — while roles not
+  listed are preserved (a managed `manager` with assigned projects is never
+  stripped). Without `role-filters` the behavior is unchanged.
+- **Unrecognized top-level config sections are reported**: cc-backend now logs a
+  warning for unknown top-level keys in `config.json`, which most often means a
+  setting was nested at the wrong level (e.g. `resampling` next to `main`
+  instead of inside it) and was silently ignored before.
+- **The `auth` section is validated again**: Its JSON schema was missing the
+  enclosing `type`/`properties` wrapper, so it accepted every input and no auth
+  option was ever checked. With the schema fixed, an incomplete auth section now
+  aborts startup — `jwts` requires `max-age`, `oidc` requires `provider`, and
+  `ldap` requires `url`, `user-base`, `search-dn`, `user-bind` and `user-filter`.
+  Each of the three subsections stays optional on its own.
+- **`archive.retention` target keys**: The retention target is configured with
+  `target-kind` and `target-path` (or the `target-*` S3 keys). The `location` key
+  used by the old example configuration was never read by the code, so a `move`
+  or `copy` policy configured that way ran against an empty target path.
+
+### New features
+
+- **Configurable footer links**: `main.footer-links` lets the Imprint and
+  Privacy Policy footer entries point at internal pages (default) or external
+  URLs. External `http(s)` targets open in a new tab; empty or unset values fall
+  back to the built-in `/imprint` and `/privacy` routes, and the existing
+  `./var/*.tmpl` override mechanism keeps working.
+- **Display smoothing for metric plots**: A centered, NaN-aware moving average
+  can be applied in the plot layer, after whatever downsampling the backend
+  performed. It preserves series length and index alignment, skips NaN/null
+  samples, keeps all-NaN windows as gaps, and shrinks the window at the series
+  edges. The window is a per-user setting in data points with a site default in
+  `ui.plot-configuration.smoothing-window` (0 disables it). It is display-only:
+  reported statistics and job footprints are unaffected.
+- **Metric tooltips**: `metricConfig` entries in `cluster.json` accept an
+  optional `tooltip` that is rendered in the metric selection dialog.
+- **Metric store statistics from cached aggregates**: Buffers maintain running
+  sum/min/max/count while data is written and compute them eagerly on checkpoint
+  load, so a full-buffer statistics request is served from the cached aggregate
+  instead of rescanning the samples.
+- **Checkpoint retention aware of running jobs**: The metric store receives a
+  `NodeProvider` (the job repository) at `Init`. Checkpoint cleanup now skips
+  nodes that still have running jobs, the full checkpoint history is loaded for
+  those nodes at startup, and this also applies to the `-cleanup-checkpoints`
+  CLI path.
+
+### Bug fixes
+
+- **Metric plots and the policy-based resample config**: `MetricPlot` still read
+  the removed `trigger`/`resolutions` values, so the array-based resolution
+  branch was unreachable and the zoom guard always fired. The zoom trigger is now
+  derived from the policy's target point count.
+- **Resample algorithm for running jobs**: The selected algorithm was not
+  forwarded to the metric store when loading data for running jobs.
+- **Partially covered buffers**: Requests that reach beyond the stored data now
+  get NaN padding at the start/end instead of misaligned series
+  (`dataNotAligned`).
+- **Data race in the statistics read path**: Reading buffer statistics no longer
+  mutates the buffer, and the fast path is guarded against empty buffers.
+- **Empty node levels leaked**: The retention free path now prunes node levels
+  that no longer hold any data, and no longer force-frees buffers that are
+  retained for running jobs.
+- **Plot render options in the wrong place**: `PlotRenderOptions` is only shown
+  in the user settings again.
+- **Invisible navbar**: Fixed a stuck animation that hid the navbar with certain
+  browser settings.
+- **Subcluster dropdown**: The subcluster selection is size-limited and scrolls
+  instead of overflowing.
+- **OIDC login session handling**: Fixed session handling on the OIDC login
+  route.
 
 ### Dependencies
 
 - **Added** `github.com/alexedwards/scs/v2` and
   `github.com/alexedwards/scs/sqlite3store`.
-- **Removed** `github.com/gorilla/sessions` (and `github.com/gorilla/securecookie`).
+- **Removed** `github.com/gorilla/sessions` (and `github.com/gorilla/securecookie`),
+  and `github.com/joho/godotenv` together with the `.env` support.
+- **Upgraded** `cc-lib` (GraphQL code regenerated) and refreshed the remaining Go
+  module dependencies.
 
 ## Changes in 1.5.4
 
@@ -286,7 +400,11 @@ This is also the default.
 
 - **cc-lib upgraded**: Updated to latest cc-lib version.
 
-## Known issues
+## Known issues (as of 1.5.2)
+
+These were the open issues at the time of the 1.5.2 release and are kept here for
+that release's record; they are not necessarily still open. Note that the
+`ui-config` section referenced below is now called `ui`.
 
 - The new dynamic memory management is not bullet proof yet across restarts.
   Buffers that are kept outside the retention period may be lost across a