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/home/home_screen.dart

@@ -12,6 +12,10 @@ class HomeScreen extends StatelessWidget {
       appBar: AppBar(title: const Text('Home')),
       body: Consumer<AuthState>(
         builder: (context, authState, child) {
+          if (authState.isLoading) {
+            return const Center(child: CircularProgressIndicator());
+          }
+
           return authState.isLoggedIn
               ? const _LoggedInView()
               : const _LoggedOutView();
@@ -40,22 +44,39 @@ class _LoggedInView extends StatelessWidget {
           ),
         ],
       ),
-      body: ListView.builder(
-        itemCount: 20, // Example items
-        itemBuilder: (context, index) {
-          return Card(
-            margin: const EdgeInsets.all(8.0),
-            child: ListTile(
-              leading: const Icon(Icons.star),
-              title: Text('Item ${index + 1}'),
-              subtitle: const Text('This is an example item.'),
-            ),
-          );
-        },
-      ),
+      body: authState.currentUser != null
+          ? ListView(
+              padding: const EdgeInsets.all(8.0),
+              children: [
+                Card(
+                  child: ListTile(
+                    leading: const Icon(Icons.person),
+                    title: Text(authState.currentUser!.displayName ?? 'User'),
+                    subtitle: Text(authState.currentUser!.phoneNumber ?? 'No phone number'),
+                  ),
+                ),
+                const Divider(),
+                ListView.builder(
+                  shrinkWrap: true,
+                  physics: const NeverScrollableScrollPhysics(),
+                  itemCount: 20, // Example items
+                  itemBuilder: (context, index) {
+                    return Card(
+                      margin: const EdgeInsets.symmetric(vertical: 4.0),
+                      child: ListTile(
+                        leading: const Icon(Icons.star),
+                        title: Text('Item ${index + 1}'),
+                        subtitle: const Text('This is an example item.'),
+                      ),
+                    );
+                  },
+                ),
+              ],
+            )
+          : const Center(child: Text('Loading user data...')),
       floatingActionButton: FloatingActionButton.extended(
-        onPressed: () {
-          authState.logout(); // Call logout method
+        onPressed: () async {
+          await authState.logout(); // Call logout method
         },
         label: const Text('Logout'),
         icon: const Icon(Icons.logout),
@@ -86,7 +107,7 @@ class _LoggedOutView extends StatelessWidget {
           const SizedBox(height: 30),
           ElevatedButton(
             onPressed: () {
-              context.go('/phone');
+              context.go('/login');
             },
             child: const Text('Login'),
           ),