Rebase services-as-hub-ia onto mobile-responsive-parity

Combine both branches into a single coherent branch:
- Full mobile responsive parity (useIsMobile, MobileCardRow, SheetForm,
  .mobile-touch-target, mobile cards, SheetForm forms, 44px targets,
  dirty-state confirm, TablePagination, refetchIntervalInBackground).
- Full services-as-hub IA (data-driven nav, service-page tab skeleton,
  new service types, Authentik directory + messaging, named dashboards,
  legacy routes 404, Observability split, Jellyseerr absorbed).

Enhancement: service tabs now use mobile-parity primitives:
- MediaTab: MobileCardRow below md (title/size/HDR/library/year) +
  TablePagination; DataTable at md+ (desktop branch preserved).
- FilesTab: MobileCardRow below md (name/type/size/modified) +
  handleRowClick; DataTable at md+.
- ServicePage: SheetForm branch below md (open-on-mount, sticky header
  + save bar, cancel navigates back to /services, dirty-state guard).
- Dashboard: single-column + section anchors below md (from mobile-parity)
  + empty-state CTA (from services-hub).
- App.tsx: useIsMobile() replaces inline matchMedia (from mobile-parity)
  + data-driven useNavItems (from services-hub).
- Backup tables (BackupAlerts/Jobs/Runs) already have MobileCardRow from
  mobile-parity; JobsTab inherits mobile behavior through its sub-components.

Conflict resolutions:
- Backend: entirely from services-hub (mobile didn't touch it).
- Deleted pages (Media/FileBrowser/Actions/Users/UsersPage/Applications/
  ObservabilityPage/BackupsPage + hooks/useUsers + tests): kept deleted
  (services-hub deleted them; content moved into service tabs).
- New service-tabs/*: from services-hub, enhanced with mobile patterns.
- App.tsx: services-hub's data-driven nav + mobile-parity's useIsMobile.
- Dashboard.tsx: merged (services-hub CTA + mobile-parity sections/anchors).
- ServicePage.tsx: services-hub's tab skeleton + mobile-parity's SheetForm.
- Primitives (useIsMobile/mobile-card/sheet-form/etc.): from mobile-parity.

117 frontend tests pass (mobile-parity's 122 - 5 deleted page tests +
services-hub's new tab/dashboard tests); 271 backend tests pass; lint/
build green both sides.

backend/src/media_library_viewer_api/main.py

@@ -21,8 +21,12 @@ from media_library_viewer_api.observability import (
     record_request,
     set_current_request_id,
 )
+from media_library_viewer_api.routers import (
+    authentik_users as authentik_users_router,
+)
 from media_library_viewer_api.routers import backups as backups_router
-from media_library_viewer_api.routers import dashboard, files, jobs, media, monitoring, tasks, users
+from media_library_viewer_api.routers import dashboard, files, jobs, media, monitoring, tasks
+from media_library_viewer_api.routers import dashboards as dashboards_router
 from media_library_viewer_api.routers import services as services_router
 from media_library_viewer_api.routers import widgets as widgets_router
 from media_library_viewer_api.routers.settings import router as settings_router
@@ -136,12 +140,13 @@ app.include_router(monitoring.router)
 app.include_router(media.router)
 app.include_router(files.router)
 app.include_router(jobs.router)
-app.include_router(users.router)
 app.include_router(tasks.router)
 app.include_router(settings_router)
 app.include_router(backups_router.router)
 app.include_router(widgets_router.router)
+app.include_router(dashboards_router.router)
 app.include_router(services_router.router)
+app.include_router(authentik_users_router.router)
 
 
 @app.get("/api/health")