fix: v2.0.4+24 — login fixes, signup toggle, forgot-password, guest SnackBar, Google OAuth

- Google Sign-In: wire serverClientId (639347358523-mtkm...apps.googleusercontent.com) so idToken is returned on Android
- Email login: raise timeout 10s→25s, add single retry on SocketException/TimeoutException
- Forgot Password: real glassmorphism bottom sheet with safe-degrade SnackBar (endpoint missing on backend)
- Create Account: same-page AnimatedSwitcher toggle with glassmorphism signup form; delete old RegisterScreen
- Desktop parity: DesktopLoginScreen same-page toggle; delete DesktopRegisterScreen
- Guest mode: remove ScaffoldMessenger SnackBar from HomeScreen outer catch (inner _safe wrappers already return [])
- LoginScreen: clearSnackBars() on postFrameCallback to prevent carried-over SnackBars from prior screens
- ProGuard: add Google Sign-In + OkHttp keep rules
- Version bump: 2.0.0+20 → 2.0.4+24; settings _appVersion → 2.0.4

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/core/api/api_endpoints.dart

@@ -15,6 +15,7 @@ class ApiEndpoints {
   static const String logout = "$baseUrl/user/logout/";
   static const String status = "$baseUrl/user/status/";
   static const String updateProfile = "$baseUrl/user/update-profile/";
+  static const String forgotPassword = "$baseUrl/user/forgot-password/";
 
   // Events
   static const String eventTypes = "$baseUrl/events/type-list/";             // list of event types