chore: archive observability-service-registry, track pi-map artifacts

- Archive the completed observability-service-registry SDD change into
  openspec/changes/archive/ (delivered across 5 slices; only
  jellyfin-service-registry remains active).
- Stop ignoring .pi-map.md / .pi-map.index.md so the navigation maps are
  versioned alongside the code, and add the regenerated map pairs repo-wide.

frontend/src/api/.pi-map.index.md

@@ -0,0 +1,25 @@
+# frontend/src/api (index)
+dir: frontend/src/api
+
+## role
+Frontend API client layer that centralizes all HTTP communication with the backend REST API.
+## parent
+index: frontend/src/.pi-map.index.md
+map: frontend/src/.pi-map.md
+## children
+-
+## files
+- backups.ts
+- client.ts
+- services.ts
+- widgets.ts
+## links
+index: frontend/src/api/.pi-map.index.md
+map: frontend/src/api/.pi-map.md
+## workflows
+- change api behavior
+  read: backups.ts, client.ts, services.ts
+- change api CLI
+  read: client.ts
+## dirty
+-

frontend/src/api/.pi-map.md

@@ -0,0 +1,32 @@
+# frontend/src/api
+dir: frontend/src/api
+
+index: frontend/src/api/.pi-map.index.md
+
+## role
+Frontend API client layer that centralizes all HTTP communication with the backend REST API.
+## files
+- backups.ts | Provides API client functions for fetching and managing backup-related data including jobs, runs, alerts, and dashboard summaries. | exp: func:fetchBackupJobs() → Promise<BackupJob[]>, call:fetch, call:res.json, raise:Error, func:fetchBackupJob(jobId: string) → Promise<{ job: BackupJob; runs: BackupRun[] }>, call:fetch, call:res.json, raise:Error, func:fetchBackupRuns(jobId: string, status: string) → Promise<BackupRun[]>, call:params.append, call:fetch, call:res.json, raise:Error, func:fetchBackupRun(runId: string) → Promise<BackupRun>, call:fetch, call:res.json, raise:Error, func:fetchBackupAlerts(jobId: string, acknowledged: boolean, severity: string) → Promise<BackupAlert[]>, call:params.append, call:String, call:fetch, call:res.json, raise:Error, func:acknowledgeBackupAlert(alertId: string) → Promise<BackupAlert>, call:fetch, call:res.json, raise:Error, func:fetchBackupDashboard() → Promise<BackupDashboardSummary>, call:fetch, call:res.json, raise:Error | dep: ../types/backups
+- client.ts | Typed API client providing fetch-based helper functions for communicating with a FastAPI backend across dashboard, monitoring, media, files, jobs, and observability endpoints. | exp: fetchCounts, fetchLibraries, fetchActivity, fetchUsers, fetchNowPlaying, fetchMonitoringMachines, fetchAppVersion, fetchDashboardShortcuts, saveDashboardShortcut, deleteDashboardShortcut, fetchMonitoringSettings, fetchSSHKeys, generateSSHKey, saveSSHKey, deleteSSHKey, fetchSavedTasks, fetchSavedTaskRuns, saveTask, deleteTask, runTask, saveMonitoringMachine, testMonitoringMachineSSH, deleteMonitoringMachine, resetLocalDatabase, fetchMediaStatus, buildMediaIndex, stopMediaIndexBuild, forceStopMediaIndexBuild, queryMedia, fetchDirectoryListing, fetchFfprobe, fetchStat, resolvePath, fetchJobTemplates, runJob, fetchUserMessageQueueStatus, sendUserMessage, fetchAlertmanagerAlerts, fetchAlertmanagerStatus, fetchGrafanaStatus, fetchPrometheusStatus, fetchPrometheusTargets | dep: ../auth, ../types
+- services.ts | Provides CRUD HTTP client functions for managing service types and service instances via a REST API. | exp: func:fetchServiceTypes() → Promise<ServiceTypeInfo[]>, call:fetch, call:res.json, raise:Error, func:fetchServiceInstances(serviceType: string) → Promise<ServiceInstance[]>, call:encodeURIComponent, call:fetch, call:res.json, raise:Error, func:createServiceInstance(input: ServiceInstanceInput) → Promise<ServiceInstance>, call:fetch, call:JSON.stringify, call:res.json, raise:Error, func:updateServiceInstance(input: ServiceInstanceInput) → Promise<ServiceInstance>, call:fetch, call:JSON.stringify, call:res.json, raise:Error, func:deleteServiceInstance(serviceId: string) → Promise<{ status: string }>, call:fetch, call:res.json, raise:Error | dep: ../types
+- widgets.ts | Provides CRUD API client functions for managing widget instances and fetching widget-related data from a REST backend. | exp: func:fetchBuiltinWidgetKinds() → Promise< BuiltinWidgetKindInfo[] >, call:fetch, call:res.json, raise:Error, func:fetchWidgetInstances() → Promise<WidgetInstance[]>, call:fetch, call:res.json, raise:Error, func:createWidgetInstance(input: WidgetInstanceInput) → Promise<WidgetInstance>, call:fetch, call:JSON.stringify, call:res.json, raise:Error, func:updateWidgetInstance(input: WidgetInstanceInput) → Promise<WidgetInstance>, call:fetch, call:JSON.stringify, call:res.json, raise:Error, func:deleteWidgetInstance(widgetId: string) → Promise<{ status: string }>, call:fetch, call:res.json, raise:Error, func:fetchWidgetData(widgetId: string) → Promise<WidgetDataResponse>, call:fetch, call:res.json, raise:Error | dep: ../types
+## arch
+Modular typed fetch-based client functions organized by domain (backups, services, widgets, general), exposing per-endpoint helper methods consumed by the UI layer.
+## tags
+fetch, call:fetch, call:res.json, raise:error, backup, widget, delete, service
+## symbols
+- fetchBackupJobs
+- fetchBackupJob
+- fetchBackupRuns
+- fetchBackupRun
+- fetchBackupAlerts
+- acknowledgeBackupAlert
+- fetchBackupDashboard
+- fetchServiceTypes
+## workflows
+- change api behavior
+  read: backups.ts, client.ts, services.ts
+- change api CLI
+  read: client.ts
+## dirty
+-