feat(fleet): add service type enum and infra scope

Replace the free-form service_type string with a ServiceType enum (ccms,
ccmc, ccb, cces, ccsa, ccnc, ccem). The short code is the canonical value
stored in the DB, the config-tree directory name and a NATS discovery
subject token; Description() gives the human-readable name.

Add a second scope alongside per-node agents: ScopeInfra covers
cluster-independent monitoring infrastructure services, which are
identified by (hostname, service_type) and carry an empty cluster.
InfraRegistry is the ScopeInfra sibling of Registry and shares the same
table, state machine and config-revision handshake. It deliberately
exposes no StartSweep: MarkStale ages rows by last_heartbeat regardless
of scope, so a single sweep goroutine per process covers both scopes.

On the repository side ServiceDB gains a Scope column and the two
queries the discovery publisher and infra enumeration need, ListActive()
and ListByScope(). ResetConnection() now also resets the fleet
repository singleton so tests get a fresh handle.

Migration 13 is edited in place rather than superseded by a new
migration: the service table is unreleased, so no existing deployment
has it yet.

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

internal/repository/fleet_test.go

@@ -0,0 +1,111 @@
+// Copyright (C) NHR@FAU, University Erlangen-Nuremberg.
+// All rights reserved. This file is part of cc-backend.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+package repository
+
+import (
+	"testing"
+)
+
+func TestFleetRepository(t *testing.T) {
+	setup(t) // migrates a fresh temp DB to the current schema version
+	repo := GetFleetRepository()
+
+	// A per-node (cluster) agent and a cluster-independent infra service.
+	clusterSvc := &ServiceDB{
+		Cluster: "fritz", Hostname: "node01", ServiceType: "agent",
+		InstanceID: "iid-cluster", Scope: "cluster", RegisteredAt: 1000,
+	}
+	infraSvc := &ServiceDB{
+		Cluster: "", Hostname: "ms01", ServiceType: "metric-store",
+		InstanceID: "iid-infra", Scope: "infra", RegisteredAt: 2000,
+	}
+
+	if _, err := repo.RegisterService(clusterSvc); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := repo.RegisterService(infraSvc); err != nil {
+		t.Fatal(err)
+	}
+
+	t.Run("ListByScope isolates infra from cluster", func(t *testing.T) {
+		infra, err := repo.ListByScope("infra")
+		noErr(t, err)
+		if len(infra) != 1 {
+			t.Fatalf("want 1 infra service, got %d", len(infra))
+		}
+		if infra[0].InstanceID != "iid-infra" || infra[0].Cluster != "" || infra[0].Scope != "infra" {
+			t.Fatalf("unexpected infra row: %+v", infra[0])
+		}
+
+		cluster, err := repo.ListByScope("cluster")
+		noErr(t, err)
+		if len(cluster) != 1 || cluster[0].InstanceID != "iid-cluster" {
+			t.Fatalf("unexpected cluster scope rows: %+v", cluster)
+		}
+	})
+
+	t.Run("ListByCluster sees only its cluster", func(t *testing.T) {
+		rows, err := repo.ListByCluster("fritz")
+		noErr(t, err)
+		if len(rows) != 1 || rows[0].InstanceID != "iid-cluster" {
+			t.Fatalf("unexpected ListByCluster(fritz): %+v", rows)
+		}
+	})
+
+	t.Run("scope round-trips through GetByInstanceID", func(t *testing.T) {
+		got, err := repo.GetByInstanceID("iid-infra")
+		noErr(t, err)
+		if got.Scope != "infra" || got.State != "pending" {
+			t.Fatalf("unexpected: scope=%q state=%q", got.Scope, got.State)
+		}
+	})
+
+	t.Run("heartbeat is instance-id keyed and scope-agnostic", func(t *testing.T) {
+		affected, err := repo.Heartbeat("iid-infra", 3000)
+		noErr(t, err)
+		if affected != 1 {
+			t.Fatalf("want 1 row affected, got %d", affected)
+		}
+		affected, err = repo.Heartbeat("does-not-exist", 3000)
+		noErr(t, err)
+		if affected != 0 {
+			t.Fatalf("want 0 rows affected for unknown instance, got %d", affected)
+		}
+	})
+
+	t.Run("ListActive returns only active services", func(t *testing.T) {
+		// iid-infra was activated by the heartbeat above; iid-cluster is still pending.
+		active, err := repo.ListActive()
+		noErr(t, err)
+		if len(active) != 1 || active[0].InstanceID != "iid-infra" || active[0].State != "active" {
+			t.Fatalf("unexpected ListActive result: %+v", active)
+		}
+	})
+
+	t.Run("config revision persists", func(t *testing.T) {
+		noErr(t, repo.SetConfigRevision("iid-infra", 42))
+		got, err := repo.GetByInstanceID("iid-infra")
+		noErr(t, err)
+		if got.ConfigRevision != 42 {
+			t.Fatalf("want config_revision 42, got %d", got.ConfigRevision)
+		}
+	})
+
+	t.Run("re-register keeps revision, resets scope and state", func(t *testing.T) {
+		// Same identity triple, but arriving as an infra registration again.
+		reReg := &ServiceDB{
+			Cluster: "", Hostname: "ms01", ServiceType: "metric-store",
+			InstanceID: "iid-infra-2", Scope: "infra", RegisteredAt: 4000,
+		}
+		if _, err := repo.RegisterService(reReg); err != nil {
+			t.Fatal(err)
+		}
+		got, err := repo.GetByInstanceID("iid-infra-2")
+		noErr(t, err)
+		if got.State != "pending" || got.Scope != "infra" || got.ConfigRevision != 42 {
+			t.Fatalf("unexpected after re-register: %+v", got)
+		}
+	})
+}