fix: resolve flutter analyze errors - remove leaked code, fix method calls, cleanup imports

lib/features/auth/presentation/login_screen.dart

@@ -1,18 +1,67 @@
 import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:go_router/go_router.dart';
 
-import '../../../shared/widgets/feature_placeholder.dart';
+import '../../../app/router/route_names.dart';
+import '../providers/auth_provider.dart';
 
-class LoginScreen extends StatelessWidget {
+class LoginScreen extends ConsumerWidget {
   const LoginScreen({super.key});
 
   @override
-  Widget build(BuildContext context) {
+  Widget build(BuildContext context, WidgetRef ref) {
+    final authState = ref.watch(authProvider);
+
+    ref.listen<AuthState>(authProvider, (_, next) {
+      if (next is AuthAuthenticated) {
+        context.go(RouteNames.home);
+      }
+    });
+
+    final isLoading = authState is AuthLoading;
+    final errorMsg = authState is AuthError ? authState.message : null;
+
     return Scaffold(
-      appBar: AppBar(title: const Text('Dang nhap')),
-      body: const FeaturePlaceholder(
-        title: 'Google Login',
-        description:
-            'Khung dang nhap Google OAuth cho mobile auth endpoint. Se bo sung token refresh va secure storage trong phase tiep theo.',
+      body: SafeArea(
+        child: Center(
+          child: Padding(
+            padding: const EdgeInsets.symmetric(horizontal: 32),
+            child: Column(
+              mainAxisSize: MainAxisSize.min,
+              children: [
+                const Icon(Icons.menu_book_rounded, size: 64),
+                const SizedBox(height: 20),
+                Text('Reader App', style: Theme.of(context).textTheme.headlineMedium),
+                const SizedBox(height: 8),
+                Text(
+                  'Đọc truyện mọi lúc, mọi nơi',
+                  style: Theme.of(context).textTheme.bodyLarge,
+                ),
+                const SizedBox(height: 48),
+                if (errorMsg != null) ...[
+                  Text(errorMsg, style: const TextStyle(color: Colors.red)),
+                  const SizedBox(height: 16),
+                ],
+                FilledButton.icon(
+                  onPressed: isLoading
+                      ? null
+                      : () => ref.read(authProvider.notifier).signInWithGoogle(),
+                  icon: isLoading
+                      ? const SizedBox(
+                          width: 18,
+                          height: 18,
+                          child: CircularProgressIndicator(strokeWidth: 2),
+                        )
+                      : const Icon(Icons.login),
+                  label: const Text('Đăng nhập bằng Google'),
+                  style: FilledButton.styleFrom(
+                    minimumSize: const Size.fromHeight(52),
+                  ),
+                ),
+              ],
+            ),
+          ),
+        ),
       ),
     );
   }