feat(app): finalize ad gated flows and weather

- add AppLogger and replace scattered print logging\n- implement ad-gated recommendation flow with reminder handling and calendar link\n- complete Bluetooth share pipeline with ad gate and merge\n- integrate KMA weather API with caching and dart-define decoding\n- add NaverUrlProcessor refactor and restore restaurant repository tests

lib/core/constants/api_keys.dart

@@ -18,6 +18,14 @@ class ApiKeys {
   static String get naverClientId => _decodeIfNeeded(_encodedClientId);
   static String get naverClientSecret => _decodeIfNeeded(_encodedClientSecret);
 
+  static const String _encodedWeatherServiceKey = String.fromEnvironment(
+    'KMA_SERVICE_KEY',
+    defaultValue: '',
+  );
+
+  static String get weatherServiceKey =>
+      _decodeIfNeeded(_encodedWeatherServiceKey);
+
   static const String naverLocalSearchEndpoint =
       'https://openapi.naver.com/v1/search/local.json';