Deliver localized auth app with verification and go_router

Integrate themed login/signup, EN/RU localization, shared dummy providers, verification recovery screens and named URL routes. Store frontend guidelines, workflow skills, validation and delivery documentation. Related to #2, #3, #5 and #6.

frontend/app/pubspec.yaml

@@ -0,0 +1,28 @@
+name: sxchnge_app
+description: SXCHNGE consumer application.
+publish_to: none
+version: 0.1.0+1
+environment:
+  sdk: '>=3.13.0 <4.0.0'
+  flutter: '>=3.47.0'
+dependencies:
+  flutter:
+    sdk: flutter
+  sxchnge_auth:
+    path: ../packages/sxchnge_auth
+  sxchnge_theme:
+    path: ../packages/sxchnge_theme
+  flutter_localizations:
+    sdk: flutter
+  intl: any
+  provider: ^6.1.5
+  shared_preferences: ^2.5.3
+  cupertino_icons: ^1.0.8
+  go_router: ^18.0.1
+dev_dependencies:
+  flutter_test:
+    sdk: flutter
+  flutter_lints: ^6.0.0
+flutter:
+  generate: true
+  uses-material-design: true