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/dependencies.py

@@ -18,7 +18,6 @@ from typing import Any
 from fastapi import HTTPException, Request
 
 from media_library_viewer_api.clients.jellyfin import JellyfinClient
-from media_library_viewer_api.clients.jellyseerr import JellyseerrClient
 from media_library_viewer_api.clients.local import LocalCommandClient
 from media_library_viewer_api.clients.ssh import RemoteSSHClient
 from media_library_viewer_api.config import get_settings
@@ -178,22 +177,6 @@ def get_jellyfin_client(request: Request = None) -> JellyfinClient:
     return _jellyfin_client_for(cache_key)
 
 
-def get_jellyseerr_client(request: Request = None) -> JellyseerrClient | None:
-    """Return a cached Jellyseerr client when configured, otherwise None."""
-    store = get_settings_store()
-    service_id = _request_jellyfin_service_id(request)
-    service = _service_record(store, "jellyseerr", service_id)
-    if service is None:
-        logger.info("Jellyseerr client not configured (no jellyseerr service)")
-        return None
-    base_url = str(service.get("config", {}).get("base_url") or "")
-    api_key = str(service.get("secrets", {}).get("api_key") or "")
-    if not base_url or not api_key:
-        logger.info("Jellyseerr service is missing base_url or api_key")
-        return None
-    return JellyseerrClient(base_url, api_key)
-
-
 def _ssh_client_from_machine_config(machine: dict[str, Any], store: SettingsStore | None = None) -> RemoteSSHClient:
     """Build a RemoteSSHClient from a machine config dict."""
     store = store or get_settings_store()