feat: add local library albums to Albums tab with unified grid and LocalAlbumScreen

- Add local library albums as clickable cards in Albums filter
- Merge downloaded and local albums into single unified grid (fix layout gaps)
- Create LocalAlbumScreen for viewing local album details with:
  - Cover art display with dominant color extraction
  - Album info card with Local badge and quality info
  - Track list with disc grouping support
  - Selection mode with delete functionality
  - UI consistent with DownloadedAlbumScreen (Card + ListTile layout)
- Add singles filter support for local library singles
- Add extractDominantColorFromFile to PaletteService
- Add delete(id) method to LibraryDatabase
- Add removeItem(id) method to LocalLibraryNotifier
- Update CHANGELOG.md for v3.4.0

android/app/src/main/kotlin/com/zarz/spotiflac/MainActivity.kt

@@ -893,6 +893,13 @@ class MainActivity: FlutterActivity() {
                             result.success(response)
                         }
                         // Local Library Scanning
+                        "setLibraryCoverCacheDir" -> {
+                            val cacheDir = call.argument<String>("cache_dir") ?: ""
+                            withContext(Dispatchers.IO) {
+                                Gobackend.setLibraryCoverCacheDirJSON(cacheDir)
+                            }
+                            result.success(null)
+                        }
                         "scanLibraryFolder" -> {
                             val folderPath = call.argument<String>("folder_path") ?: ""
                             val response = withContext(Dispatchers.IO) {