refactor: Update Twitter OAuth 2.0 PKCE flow for dynamic redirect URI and public client authentication, replace SVG back button with a native icon, and enhance Twitter login error reporting.

lib/core/services/twitter_auth_service.dart

@@ -3,14 +3,20 @@ import 'dart:math';
 
 import 'package:crypto/crypto.dart';
 import 'package:dio/dio.dart';
+import 'package:real_estate_mobile/config/app_config.dart';
 
 /// Twitter OAuth 2.0 PKCE flow for mobile.
 class TwitterAuthService {
   static const _clientId = 'eWEzaDJ0al9lX1diOGY0ejRYeXM6MTpjaQ';
-  // Must match the callback URL configured in Twitter Developer Portal
-  static const _redirectUri = 'https://dev.re-quest.com/auth/callback/twitter';
   static const _scope = 'tweet.read users.read offline.access';
 
+  /// Derive redirect URI from API base URL (matches next-auth callback)
+  static String get _redirectUri {
+    final apiUrl = AppConfig.apiBaseUrl; // e.g. https://dev.re-quest.com/api/v1
+    final base = apiUrl.replaceAll(RegExp(r'/api/v1/?$'), '');
+    return '$base/api/auth/callback/twitter';
+  }
+
   late final String _codeVerifier;
   late final String _codeChallenge;
   late final String _stateParam;
@@ -51,21 +57,20 @@ class TwitterAuthService {
   Future<Map<String, dynamic>?> exchangeCodeForUser(String code) async {
     final dio = Dio();
 
-    // Exchange code for access token
+    // Exchange code for access token (PKCE public client — client_id in body)
+    final tokenBody =
+        'code=${Uri.encodeComponent(code)}'
+        '&grant_type=authorization_code'
+        '&client_id=${Uri.encodeComponent(_clientId)}'
+        '&redirect_uri=${Uri.encodeComponent(_redirectUri)}'
+        '&code_verifier=${Uri.encodeComponent(_codeVerifier)}';
+
     final tokenResponse = await dio.post(
       'https://api.twitter.com/2/oauth2/token',
       options: Options(
         contentType: 'application/x-www-form-urlencoded',
-        headers: {
-          'Authorization': 'Basic ${base64Encode(utf8.encode('$_clientId:'))}',
-        },
       ),
-      data: {
-        'code': code,
-        'grant_type': 'authorization_code',
-        'redirect_uri': _redirectUri,
-        'code_verifier': _codeVerifier,
-      },
+      data: tokenBody,
     );
 
     final accessToken = tokenResponse.data['access_token'] as String?;

lib/core/widgets/app_bottom_nav_bar.dart

@@ -5,6 +5,7 @@ import 'package:go_router/go_router.dart';
 import 'package:real_estate_mobile/core/constants/app_colors.dart';
 import 'package:real_estate_mobile/features/auth/presentation/providers/auth_provider.dart';
 import 'package:real_estate_mobile/features/home/presentation/screens/home_screen.dart';
+import 'package:real_estate_mobile/features/messaging/presentation/providers/messaging_provider.dart';
 
 /// Determines which tab is active based on the current route.
 int _currentTabIndex(BuildContext context) {
@@ -78,19 +79,26 @@ class AppBottomNavBar extends ConsumerWidget {
                   }
                 },
               ),
-              _NavItem(
-                svgPath: 'assets/icons/nav_messages_icon.svg',
-                fallbackIcon: Icons.chat_bubble,
-                isSelected: selectedIndex == 2,
-                onTap: () {
-                  final authState = ref.read(authProvider);
-                  if (authState.status != AuthStatus.authenticated) {
-                    context.push('/login');
-                    return;
-                  }
-                  context.go('/messages');
-                },
-              ),
+              Builder(builder: (context) {
+                final authState = ref.watch(authProvider);
+                final isAuth = authState.status == AuthStatus.authenticated;
+                final msgUnread = isAuth
+                    ? ref.watch(messagingProvider).unreadCount
+                    : 0;
+                return _NavItem(
+                  svgPath: 'assets/icons/nav_messages_icon.svg',
+                  fallbackIcon: Icons.chat_bubble,
+                  isSelected: selectedIndex == 2,
+                  badgeCount: msgUnread,
+                  onTap: () {
+                    if (!isAuth) {
+                      context.push('/login');
+                      return;
+                    }
+                    context.go('/messages');
+                  },
+                );
+              }),
               _NavItem(
                 svgPath: 'assets/icons/nav_profile_icon.svg',
                 fallbackIcon: Icons.person_outline,
@@ -117,12 +125,14 @@ class _NavItem extends StatelessWidget {
   final IconData fallbackIcon;
   final bool isSelected;
   final VoidCallback onTap;
+  final int badgeCount;
 
   const _NavItem({
     required this.svgPath,
     required this.fallbackIcon,
     required this.isSelected,
     required this.onTap,
+    this.badgeCount = 0,
   });
 
   @override
@@ -132,20 +142,50 @@ class _NavItem extends StatelessWidget {
       behavior: HitTestBehavior.opaque,
       child: Padding(
         padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 8),
-        child: SvgPicture.asset(
-          svgPath,
-          width: 24,
-          height: 24,
-          colorFilter: isSelected
-              ? const ColorFilter.mode(
-                  AppColors.primaryDark, BlendMode.srcIn)
-              : const ColorFilter.mode(
-                  AppColors.accentOrange, BlendMode.srcIn),
-          placeholderBuilder: (_) => Icon(
-            fallbackIcon,
-            size: 24,
-            color: isSelected ? AppColors.primaryDark : AppColors.accentOrange,
-          ),
+        child: Stack(
+          clipBehavior: Clip.none,
+          children: [
+            SvgPicture.asset(
+              svgPath,
+              width: 24,
+              height: 24,
+              colorFilter: isSelected
+                  ? const ColorFilter.mode(
+                      AppColors.primaryDark, BlendMode.srcIn)
+                  : const ColorFilter.mode(
+                      AppColors.accentOrange, BlendMode.srcIn),
+              placeholderBuilder: (_) => Icon(
+                fallbackIcon,
+                size: 24,
+                color:
+                    isSelected ? AppColors.primaryDark : AppColors.accentOrange,
+              ),
+            ),
+            if (badgeCount > 0)
+              Positioned(
+                top: -6,
+                right: -8,
+                child: Container(
+                  padding:
+                      const EdgeInsets.symmetric(horizontal: 4, vertical: 1),
+                  constraints: const BoxConstraints(minWidth: 16),
+                  decoration: BoxDecoration(
+                    color: Colors.red,
+                    borderRadius: BorderRadius.circular(8),
+                  ),
+                  child: Text(
+                    badgeCount > 99 ? '99+' : '$badgeCount',
+                    textAlign: TextAlign.center,
+                    style: const TextStyle(
+                      fontFamily: 'Fractul',
+                      fontSize: 10,
+                      fontWeight: FontWeight.w700,
+                      color: Colors.white,
+                    ),
+                  ),
+                ),
+              ),
+          ],
         ),
       ),
     );