refactor: implement Flutter best practices and proper architecture

- Create proper service layer with AuthService and FirebaseAuthService
- Implement UserModel for proper data representation
- Enhance AuthState with proper loading states and error handling
- Convert stateless widgets to stateful where appropriate
- Add proper form validation and user feedback mechanisms
- Implement comprehensive error handling and loading indicators
- Fix redirect logic in router for proper authentication flow
- Create theme system with light and dark themes
- Add shared components like LoadingIndicator
- Improve code organization following recommended architecture
- Add proper disposal of controllers and focus nodes
- Implement proper null safety handling

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

lib/profile/profile_screen.dart

@@ -7,17 +7,66 @@ class ProfileScreen extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final authState = Provider.of<AuthState>(context, listen: false);
+    final authState = Provider.of<AuthState>(context);
 
     return Scaffold(
       appBar: AppBar(title: const Text('Profile')),
-      body: Center(
-        child: ElevatedButton(
-          onPressed: () {
-            authState.toggleLogin();
-          },
-          child: const Text('Logout'),
-        ),
+      body: authState.currentUser != null
+          ? Padding(
+              padding: const EdgeInsets.all(16.0),
+              child: Column(
+                crossAxisAlignment: CrossAxisAlignment.start,
+                children: [
+                  CircleAvatar(
+                    radius: 50,
+                    child: Text(
+                      authState.currentUser!.displayName != null
+                          ? authState.currentUser!.displayName![0].toUpperCase()
+                          : '?',
+                      style: const TextStyle(fontSize: 30),
+                    ),
+                  ),
+                  const SizedBox(height: 16),
+                  _buildProfileItem('Name', authState.currentUser!.displayName ?? 'Not set'),
+                  _buildProfileItem('Phone', authState.currentUser!.phoneNumber ?? 'Not set'),
+                  _buildProfileItem('Email', authState.currentUser!.email ?? 'Not set'),
+                  const Spacer(),
+                  Center(
+                    child: authState.isLoading
+                        ? const CircularProgressIndicator()
+                        : ElevatedButton.icon(
+                            onPressed: () async {
+                              await authState.logout();
+                            },
+                            icon: const Icon(Icons.logout),
+                            label: const Text('Logout'),
+                            style: ElevatedButton.styleFrom(
+                              backgroundColor: Colors.red,
+                              foregroundColor: Colors.white,
+                            ),
+                          ),
+                  ),
+                ],
+              ),
+            )
+          : const Center(child: Text('Loading...')),
+    );
+  }
+
+  Widget _buildProfileItem(String label, String value) {
+    return Padding(
+      padding: const EdgeInsets.only(bottom: 16.0),
+      child: Column(
+        crossAxisAlignment: CrossAxisAlignment.start,
+        children: [
+          Text(
+            label,
+            style: const TextStyle(fontWeight: FontWeight.bold, fontSize: 16),
+          ),
+          const SizedBox(height: 4),
+          Text(value.isEmpty ? 'Not set' : value),
+          const Divider(),
+        ],
       ),
     );
   }