feat(api): add /api/lidarr/search proxy with library/request enrichment

Implements GET /api/lidarr/search?q=&kind=artist|album|track. Validates
kind and q, loads lidarr_config per-request, calls the matching Lidarr
Lookup* method, enriches each result with in_library (EXISTS by MBID
against artists/albums/tracks) and requested (HasNonTerminalRequestForMBID),
and returns a normalized JSON array. Adds lidarrCfg field to handlers struct
and threads lidarrconfig.Service through Mount and server.Router.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/api/library_test.go

@@ -441,7 +441,7 @@ func TestRoutesRegisteredInMount(t *testing.T) {
 	r := chi.NewRouter()
 	w := playevents.NewWriter(h.pool, slog.New(slog.NewTextHandler(io.Discard, nil)),
 		30*time.Minute, 0.5, 30000)
-	Mount(r, h.pool, h.logger, w, config.RecommendationConfig{RadioSize: 50, RadioSizeMax: 200, RecentlyPlayedHours: 1})
+	Mount(r, h.pool, h.logger, w, config.RecommendationConfig{RadioSize: 50, RadioSizeMax: 200, RecentlyPlayedHours: 1}, h.lidarrCfg)
 
 	paths := []string{
 		"/api/artists",