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/components/cover-grid/album-selection.ts

@@ -1,4 +1,8 @@
-import { GetAlbumTracks } from '@go/library/Library';
+import {
+    GetAlbumTracks,
+    GetAlbumTracksByLibrary,
+} from '@go/library/Library';
+import { libraryStore } from '@store/library-store';
 import type { library } from '@go/models';
 import type { CoverArtUrls } from '@components/track-details/track-details.js';
 
@@ -43,6 +47,21 @@ export class AlbumSelectionManager {
         this.albumFilePathCache.clear();
     }
 
+    /**
+     * Fetch album tracks respecting the active
+     * library filter.
+     */
+    private fetchAlbumTracks(
+        albumId: number,
+    ): Promise<library.Track[]> {
+        const libId =
+            libraryStore.getSelectedLibraryId();
+
+        return libId !== null
+            ? GetAlbumTracksByLibrary(albumId, libId)
+            : GetAlbumTracks(albumId);
+    }
+
     // ================================================================
     // Album selection helpers
     // ================================================================
@@ -134,9 +153,8 @@ export class AlbumSelectionManager {
         album: library.Album,
     ): Promise<string[]> {
         try {
-            const tracks = await GetAlbumTracks(
-                album.ID,
-            );
+            const tracks =
+                await this.fetchAlbumTracks(album.ID);
 
             return tracks.map((t) => t.FilePath);
         } catch (error) {
@@ -174,9 +192,10 @@ export class AlbumSelectionManager {
             if (!album) continue;
 
             try {
-                const tracks = await GetAlbumTracks(
-                    album.ID,
-                );
+                const tracks =
+                    await this.fetchAlbumTracks(
+                        album.ID,
+                    );
 
                 // Only store if still selected.
                 if (selectedAlbums.has(album.ID)) {

frontend/src/components/cover-grid/cover-grid.ts

@@ -11,7 +11,10 @@ import type {
     VisibilityChangedEvent,
 } from '@lit-labs/virtualizer';
 import { grid } from '@lit-labs/virtualizer/layouts/grid.js';
-import { GetAlbumTracks } from '@go/library/Library';
+import {
+    GetAlbumTracks,
+    GetAlbumTracksByLibrary,
+} from '@go/library/Library';
 import { library } from '@go/models';
 import { LibraryController } from '@store/controllers/library-controller';
 import { SearchController } from '@store/controllers/search-controller';
@@ -973,9 +976,15 @@ export class CoverGrid
         this.lastSelectedTrackIndex = null;
 
         try {
-            const tracks = await GetAlbumTracks(
-                album.ID,
-            );
+            const libId =
+                this.libraryCtrl.selectedLibraryId;
+
+            const tracks = libId !== null
+                ? await GetAlbumTracksByLibrary(
+                      album.ID,
+                      libId,
+                  )
+                : await GetAlbumTracks(album.ID);
 
             if (this.expandedAlbumId === album.ID) {
                 this.expandedTracks = tracks;