refactor: integrate SearchService into MediaHandler

Update MediaHandler to use new SearchService:

Changes:
- Add searchService field to MediaHandler struct
- Instantiate SearchService in NewMediaHandler constructor
- Follows established pattern (FiltersService, CollectionService)
- Keeps handler dependencies self-contained, no main.go changes needed

Design rationale:
- Handler owns its service dependencies
- Simpler initialization than passing from main.go
- More testable with direct service instantiation
- Consistent with existing codebase patterns

Next steps: Handler methods will delegate to searchService for
search operations (implementation in follow-up commits).

internal/handlers/media.go

@@ -91,12 +91,14 @@ type MediaHandler struct {
 	db             *database.Queries
 	worker         *services.Worker
 	libraryService *services.LibraryService
+	searchService  *services.SearchService
 }
 
 func NewMediaHandler(db *database.Queries, libraryService *services.LibraryService, worker ...*services.Worker) *MediaHandler {
 	mh := &MediaHandler{
 		db:             db,
 		libraryService: libraryService,
+		searchService:  services.NewSearchService(db),
 	}
 	if len(worker) > 0 && worker[0] != nil {
 		mh.worker = worker[0]