feat(requests): show ingest progress while requests are in flight

After Lidarr accepts a request the local reconciler imports albums and
tracks as they arrive — but until the request hit 'completed' the
operator had no way to see "is anything happening?" The /requests and
/admin/requests rows now surface a live progress line whenever the
request's matched entity has children in our library.

Backend:
- New CountAlbumsByArtist + CountTracksByArtist sqlc queries.
- requestView gains imported_album_count and imported_track_count.
- New fillProgress helper computes them from the matched entity:
  - kind=artist  → counts albums + tracks under matched_artist_id
  - kind=album   → counts tracks under matched_album_id
  - kind=track   → 1 once matched_track_id is set
  N+1 in the list endpoints; acceptable at admin scale.
- handleListRequests, handleGetRequest, and handleListAdminRequests
  populate the new fields on every response.

Frontend:
- LidarrRequest TS type extended with the two counters.
- Both the operator's /requests page and the admin /admin/requests
  page render an accent-colored line under the row meta when at
  least one counter is non-zero, e.g.:
    Artist:  "5 albums · 47 tracks ingested"
    Album:   "12 tracks ingested"
    Track:   "Track ingested"
- Updated test fixtures to include the new required fields.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/db/queries/tracks.sql

@@ -90,3 +90,9 @@ WHERE t.artist_id = $1
   )
 ORDER BY albums.release_date NULLS LAST, albums.sort_title,
          t.disc_number NULLS FIRST, t.track_number NULLS FIRST, t.id;
+
+-- name: CountTracksByArtist :one
+-- Used by request-progress reporting to count tracks ingested under a
+-- matched artist (sum across all the artist's albums) while a request
+-- is still in flight.
+SELECT COUNT(*) FROM tracks WHERE artist_id = $1;