refactor: remove Qobuz from built-in provider registry, add retired provider detection

Empty the builtInProviderRegistry now that all built-in providers are
retired. Introduce isRetiredBuiltInDownloadProvider and
isRetiredBuiltInMetadataProvider to classify deezer/qobuz/tidal/spotify
as retired, replacing ad-hoc string checks. Add Dart-side metadata
provider priority reconciliation that replaces retired providers with
extensions declaring replacesBuiltInProviders. Remove getQobuzMetadata
from native bridges and platform_bridge.dart. Update crowdin.yml with
additional locale mappings.

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

@@ -2889,14 +2889,6 @@ class MainActivity: FlutterFragmentActivity() {
                             }
                             result.success(response)
                         }
-                        "getQobuzMetadata" -> {
-                            val resourceType = call.argument<String>("resource_type") ?: ""
-                            val resourceId = call.argument<String>("resource_id") ?: ""
-                            val response = withContext(Dispatchers.IO) {
-                                Gobackend.getQobuzMetadata(resourceType, resourceId)
-                            }
-                            result.success(response)
-                        }
                         "getProviderMetadata" -> {
                             val providerId = call.argument<String>("provider_id") ?: ""
                             val resourceType = call.argument<String>("resource_type") ?: ""