feat(jellyseer): sortable/filterable requests table on the Requests tab

Replace the static "recent requests" list with a proper table of all Jellyseerr
requests, sorted by date added (newest first by default) with standard sorting
and filtering.

Backend:
- JellyseerrClient.requests(max_count=500): paginated GET /api/v1/request
  (sort=added), mapped with type (movie/tv), status, media_status, and
  created_at labels. Returns up to 500 so the table can sort/filter client-side.
- fetch_jellyseer_requests(service) reuses the per-service cached client
  (shared with the stats widgets).
- new GET /api/jellyseerr/requests endpoint.

Frontend:
- JellyseerRequestsTable: TanStack Table (sorting via getSortedRowModel,
  pagination via getPaginationRowModel) reusing the Table primitives +
  TablePagination. Columns: Name / Type / Status / Media / Requested, all
  sortable; default sort Requested desc. A search box filters by name and a
  status dropdown defaults to "Open" (pending+approved+processing) with
  All/Pending/Approved/Declined options. (The shared DataTable is deliberately
  visibility-only, so this is a dedicated sortable table.)
- RequestsTab renders the stats grid + the new table (the compact recent list
  stays on the Requests overview widget).
- useJellyseerRequests hook + fetchJellyseerRequests API client.

Tests: client requests() mapping + single-page stop; fetch helper not-configured;
RequestsTab test mocks both hooks. 404/404 backend + 184/184 frontend pass;
build (tsc -b && vite build) + ESLint clean.

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

@@ -2,7 +2,7 @@
 dir: frontend/src/api
 
 ## role
-Typed API client layer that centralizes all backend communication for the frontend application across multiple service domains.
+Frontend API client layer that centralizes typed HTTP requests to backend services and external integrations.
 ## parent
 index: frontend/src/.pi-map.index.md
 map: frontend/src/.pi-map.md