feat(frontend): add multi-language support (en, zh-Hans, zh-Hant, ja)

frontend/pubspec.yaml

@@ -42,6 +42,9 @@ dependencies:
   web_socket_channel: ^3.0.3
   permission_handler: ^12.0.1
   rtmp_streaming: ^1.0.5
+  intl: ^0.20.2
+  flutter_localizations:
+    sdk: flutter
 
 dev_dependencies:
   flutter_test:
@@ -75,6 +78,7 @@ flutter_launcher_icons:
 
 # The following section is specific to Flutter packages.
 flutter:
+  generate: true
 
   # The following line ensures that the Material Icons font is
   # included with your application, so that you can use the icons in