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/screens/home_screen.dart

@@ -1,7 +1,7 @@
 // lib/screens/home_screen.dart
 import 'dart:async';
 import 'dart:ui';
-import '../core/utils/error_utils.dart';
+import 'package:flutter/foundation.dart' show kDebugMode, debugPrint;
 import 'package:flutter/material.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 import '../core/auth/auth_guard.dart';
@@ -137,10 +137,8 @@ class _HomeScreenState extends State<HomeScreen> with SingleTickerProviderStateM
         });
       }
     } catch (e) {
-      if (mounted) {
-        setState(() => _loading = false);
-        ScaffoldMessenger.of(context).showSnackBar(SnackBar(content: Text(userFriendlyError(e))));
-      }
+      if (kDebugMode) debugPrint('HomeScreen init unexpected error: $e');
+      if (mounted) setState(() => _loading = false);
     }
 
     // Refresh notification badge count (fire-and-forget)