feat(13-02): add library filter dropdown and wire all views to respect active filter

- Add selectedLibraryId state + ByLibrary conditional calls to library-store
- Add library filter pass-through methods to library-controller
- Create library-filter dropdown component in top bar
- Wire genre-details, cover-grid, artists-view, genres-view to use ByLibrary queries
- Update album-selection helper to respect library filter
- Regenerate Wails bindings for new ByLibrary methods
- Search remains client-side (automatically filtered by loaded data)
- Playlists remain unfiltered (use separate playlist store)

frontend/src/store/controllers/library-controller.ts

@@ -129,6 +129,22 @@ export class LibraryController implements ReactiveController {
         libraryStore.setScrollPosition(view, offset);
     }
 
+    // ===================================================================
+    // LIBRARY FILTER
+    // ===================================================================
+
+    get selectedLibraryId(): number | null {
+        return libraryStore.getSelectedLibraryId();
+    }
+
+    setSelectedLibrary(id: number | null): void {
+        libraryStore.setSelectedLibrary(id);
+    }
+
+    async getLibraries(): Promise<library.Info[]> {
+        return libraryStore.getLibraries();
+    }
+
     // ===================================================================
     // COVER SIZE
     // ===================================================================