fix(tests): initialize missing handlers in test setup

Fix nil pointer panics in integration tests by initializing the
four refactored handlers (MediaHandler, SearchHandler, MatchingHandler,
CollectionHandler) that were added during Phase 6 refactoring but
never added to the test setup.

These handlers were properly instantiated in cmd/server/main.go
(commit 9fd8a39) but were missing from cmd/server/tests/test_helpers.go,
causing panics when tests tried to use /api/collections and /api/media-items
endpoints.

Changes:
- Create worker with 3 concurrent workers
- Initialize CollectionHandler with queries and connManager
- Initialize MediaHandler with queries and worker
- Initialize SearchHandler with queries
- Initialize MatchingHandler with queries and connManager
- Add all four handlers to router.Config struct

Fixes panic errors:
- internal/handlers/collections.go:78 (CreateCollection nil pointer)
- internal/handlers/media.go:891 (CreateMediaItem nil pointer)

Tests now pass:
- TestCollectionsBulkOperations: PASS
- TestAnalytics*: PASS (all analytics tests)

Note: Bruno API tests and frontend were NOT affected as they use the
real running application (which has complete handler setup).

cmd/server/tests/test_helpers.go

@@ -144,6 +144,13 @@ func setupTestServer(t *testing.T) (*httptest.Server, *database.Queries, *config
 	analyticsHandler := handlers.NewAnalyticsHandler(queries)
 	queueHandler := handlers.NewQueueHandler(queries, queueProcessor)
 
+	// Create refactored handlers (matching main.go Phase 6)
+	worker := services.NewWorker(3)
+	collectionHandler := handlers.NewCollectionHandler(queries, connManager)
+	mediaHandler := handlers.NewMediaHandler(queries, worker)
+	searchHandler := handlers.NewSearchHandler(queries)
+	matchingHandler := handlers.NewMatchingHandler(queries, connManager)
+
 	// Create conversion service for OPDS
 	conversionService := services.NewConversionService(queries, getCachePath())
 	opdsHandler := handlers.NewOPDSHandler(queries, conversionService)
@@ -172,11 +179,15 @@ func setupTestServer(t *testing.T) (*httptest.Server, *database.Queries, *config
 		AuthHandler:          authHandler,
 		LibraryHandler:       libraryHandler,
 		DeviceHandler:        deviceHandler,
+		MediaHandler:         mediaHandler,
+		SearchHandler:        searchHandler,
+		MatchingHandler:      matchingHandler,
 		KOReaderHandler:      koreaderHandler,
 		WSHandler:            wsHandler,
 		ConflictHandler:      conflictHandler,
 		AnalyticsHandler:     analyticsHandler,
 		QueueHandler:         queueHandler,
+		CollectionHandler:    collectionHandler,
 		OPDSHandler:          opdsHandler,
 		ConnManager:          connManager,
 		QueueProcessor:       queueProcessor,