Fix medium-severity issues from follow-up security audit

Addresses the remaining medium findings from the second-pass audit:

- DoS hardening: bound GraphQL query cost with FixedComplexityLimit, and
  reject non-positive items-per-page / page values so uint64 conversion
  cannot underflow into an unbounded LIMIT/OFFSET. The -1 "load all"
  sentinel stays valid for dashboards; REST now returns 400 for bad input.

- Security headers: add X-Content-Type-Options, X-Frame-Options,
  Referrer-Policy and a conservative CSP (frame-ancestors/object-src/
  base-uri) that hardens against clickjacking and base-tag injection
  without restricting the self-hosted SPA's inline scripts.

- Stored XSS: render job.metaData.message as escaped text instead of
  {@html ...} in Job.root and JobFootprint, preserving line breaks via
  white-space: pre-wrap.

- SQL injection hardening: parameterize the tag-scope IN list and the
  manager project subquery in CountTags instead of interpolating
  user.Username / user.Projects (externally sourced via OIDC/LDAP).

- CSRF defense-in-depth: reject cross-site state-changing requests via
  Sec-Fetch-Site, failing open for non-browser clients, on top of the
  existing SameSite=Lax session cookie.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Entire-Checkpoint: de7d47a85c7c

internal/api/job.go

@@ -166,6 +166,10 @@ func (api *RestAPI) getJobs(rw http.ResponseWriter, r *http.Request) {
 				handleError(err, http.StatusBadRequest, rw)
 				return
 			}
+			if x < 1 {
+				handleError(fmt.Errorf("page must be >= 1"), http.StatusBadRequest, rw)
+				return
+			}
 			page.Page = x
 		case "items-per-page":
 			x, err := strconv.Atoi(vals[0])
@@ -173,6 +177,10 @@ func (api *RestAPI) getJobs(rw http.ResponseWriter, r *http.Request) {
 				handleError(err, http.StatusBadRequest, rw)
 				return
 			}
+			if x < 1 {
+				handleError(fmt.Errorf("items-per-page must be >= 1"), http.StatusBadRequest, rw)
+				return
+			}
 			page.ItemsPerPage = x
 		case "with-metadata":
 			withMetadata = true

internal/repository/jobQuery.go

@@ -76,8 +76,15 @@ func (r *JobRepository) QueryJobs(
 	}
 
 	if page != nil && page.ItemsPerPage != -1 {
+		// -1 is the only valid non-positive value ("load all"); reject other
+		// non-positive values so that uint64(page.ItemsPerPage) cannot underflow
+		// into a huge limit. Clamp Page to >= 1 to avoid the same on the offset.
+		if page.ItemsPerPage < 1 {
+			return nil, fmt.Errorf("invalid items-per-page value: %d", page.ItemsPerPage)
+		}
+		p := max(page.Page, 1)
 		limit := uint64(page.ItemsPerPage)
-		query = query.Offset((uint64(page.Page) - 1) * limit).Limit(limit)
+		query = query.Offset((uint64(p) - 1) * limit).Limit(limit)
 	}
 
 	for _, f := range filters {

internal/repository/tags.go

@@ -311,26 +311,33 @@ func (r *JobRepository) CountTags(user *schema.User) (tags []schema.Tag, counts
 		LeftJoin("jobtag jt ON t.id = jt.tag_id").
 		GroupBy("t.tag_type, t.tag_name")
 
-	// Build scope list for filtering
-	var scopeBuilder strings.Builder
-	scopeBuilder.WriteString(`"global"`)
+	// Build scope list for filtering. Values are parameterized rather than
+	// interpolated because user.Username originates from external identity
+	// providers (OIDC/LDAP) and must not be trusted as SQL.
+	scopes := []string{"global"}
 	if user != nil {
-		scopeBuilder.WriteString(`,"`)
-		scopeBuilder.WriteString(user.Username)
-		scopeBuilder.WriteString(`"`)
+		scopes = append(scopes, user.Username)
 		if user.HasAnyRole([]schema.Role{schema.RoleAdmin, schema.RoleSupport}) {
-			scopeBuilder.WriteString(`,"admin"`)
+			scopes = append(scopes, "admin")
 		}
 	}
-	q = q.Where("t.tag_scope IN (" + scopeBuilder.String() + ")")
+	q = q.Where(sq.Eq{"t.tag_scope": scopes})
 
 	// Handle Job Ownership
 	if user != nil && user.HasAnyRole([]schema.Role{schema.RoleAdmin, schema.RoleSupport}) { // ADMIN || SUPPORT: Count all jobs
 		// cclog.Debug("CountTags: User Admin or Support -> Count all Jobs for Tags")
 		// Unchanged: Needs to be own case still, due to UserRole/NoRole compatibility handling in else case
-	} else if user != nil && user.HasRole(schema.RoleManager) { // MANAGER: Count own jobs plus project's jobs
-		// Build ("project1", "project2", ...) list of variable length directly in SQL string
-		q = q.Where("jt.job_id IN (SELECT id FROM job WHERE job.hpc_user = ? OR job.project IN (\""+strings.Join(user.Projects, "\",\"")+"\"))", user.Username)
+	} else if user != nil && user.HasRole(schema.RoleManager) && len(user.Projects) > 0 { // MANAGER: Count own jobs plus project's jobs
+		// Build a parameterized ("?", "?", ...) placeholder list for the
+		// variable-length project set instead of interpolating values into SQL.
+		args := make([]any, 0, len(user.Projects)+1)
+		args = append(args, user.Username)
+		placeholders := make([]string, len(user.Projects))
+		for i, p := range user.Projects {
+			placeholders[i] = "?"
+			args = append(args, p)
+		}
+		q = q.Where("jt.job_id IN (SELECT id FROM job WHERE job.hpc_user = ? OR job.project IN ("+strings.Join(placeholders, ",")+"))", args...)
 	} else if user != nil { // USER OR NO ROLE (Compatibility): Only count own jobs
 		q = q.Where("jt.job_id IN (SELECT id FROM job WHERE job.hpc_user = ?)", user.Username)
 	}