feat: API 인증 시스템 구현 및 로그인 화면 연동

- AuthService, AuthRemoteDataSource 구현
- JWT 토큰 관리 (SecureStorage 사용)
- 로그인 화면 API 연동 및 에러 처리
- freezed 패키지로 Auth 관련 DTO 모델 생성
- 의존성 주입 설정 업데이트

lib/screens/login/widgets/login_view_redesign.dart

@@ -27,10 +27,7 @@ class _LoginViewRedesignState extends State<LoginViewRedesign>
   late AnimationController _slideController;
   late Animation<Offset> _slideAnimation;
 
-  final _usernameController = TextEditingController();
-  final _passwordController = TextEditingController();
   bool _rememberMe = false;
-  bool _isLoading = false;
 
   @override
   void initState() {
@@ -66,39 +63,23 @@ class _LoginViewRedesignState extends State<LoginViewRedesign>
   void dispose() {
     _fadeController.dispose();
     _slideController.dispose();
-    _usernameController.dispose();
-    _passwordController.dispose();
     super.dispose();
   }
 
   Future<void> _handleLogin() async {
-    if (_usernameController.text.isEmpty || _passwordController.text.isEmpty) {
-      ScaffoldMessenger.of(context).showSnackBar(
-        SnackBar(
-          content: Text('사용자명과 비밀번호를 입력해주세요.'),
-          backgroundColor: ShadcnTheme.destructive,
-        ),
-      );
-      return;
+    final success = await widget.controller.login();
+    if (success) {
+      widget.onLoginSuccess();
     }
-
-    setState(() {
-      _isLoading = true;
-    });
-
-    // 실제 로그인 로직 (임시로 2초 대기)
-    await Future.delayed(const Duration(seconds: 2));
-
-    setState(() {
-      _isLoading = false;
-    });
-
-    widget.onLoginSuccess();
   }
 
   @override
   Widget build(BuildContext context) {
-    return Scaffold(
+    return ChangeNotifierProvider.value(
+      value: widget.controller,
+      child: Consumer<LoginController>(
+        builder: (context, controller, _) {
+          return Scaffold(
       backgroundColor: ShadcnTheme.background,
       body: SafeArea(
         child: Center(
@@ -128,6 +109,8 @@ class _LoginViewRedesignState extends State<LoginViewRedesign>
             ),
           ),
         ),
+      );
+        },
       ),
     );
   }
@@ -190,6 +173,7 @@ class _LoginViewRedesignState extends State<LoginViewRedesign>
   }
 
   Widget _buildLoginCard() {
+    final controller = context.watch<LoginController>();
     return ShadcnCard(
       padding: const EdgeInsets.all(ShadcnTheme.spacing8),
       child: Column(
@@ -210,7 +194,7 @@ class _LoginViewRedesignState extends State<LoginViewRedesign>
           ShadcnInput(
             label: '사용자명',
             placeholder: '사용자명을 입력하세요',
-            controller: _usernameController,
+            controller: controller.idController,
             prefixIcon: const Icon(Icons.person_outline),
             keyboardType: TextInputType.text,
           ),
@@ -220,7 +204,7 @@ class _LoginViewRedesignState extends State<LoginViewRedesign>
           ShadcnInput(
             label: '비밀번호',
             placeholder: '비밀번호를 입력하세요',
-            controller: _passwordController,
+            controller: controller.pwController,
             prefixIcon: const Icon(Icons.lock_outline),
             obscureText: true,
             keyboardType: TextInputType.visiblePassword,
@@ -231,11 +215,9 @@ class _LoginViewRedesignState extends State<LoginViewRedesign>
           Row(
             children: [
               Checkbox(
-                value: _rememberMe,
+                value: controller.saveId,
                 onChanged: (value) {
-                  setState(() {
-                    _rememberMe = value ?? false;
-                  });
+                  controller.setSaveId(value ?? false);
                 },
                 activeColor: ShadcnTheme.primary,
               ),
@@ -244,6 +226,38 @@ class _LoginViewRedesignState extends State<LoginViewRedesign>
             ],
           ),
           const SizedBox(height: ShadcnTheme.spacing8),
+          
+          // 에러 메시지 표시
+          if (controller.errorMessage != null)
+            Container(
+              padding: const EdgeInsets.all(ShadcnTheme.spacing3),
+              margin: const EdgeInsets.only(bottom: ShadcnTheme.spacing4),
+              decoration: BoxDecoration(
+                color: ShadcnTheme.destructive.withOpacity(0.1),
+                borderRadius: BorderRadius.circular(ShadcnTheme.borderRadius),
+                border: Border.all(
+                  color: ShadcnTheme.destructive.withOpacity(0.3),
+                ),
+              ),
+              child: Row(
+                children: [
+                  Icon(
+                    Icons.error_outline,
+                    size: 20,
+                    color: ShadcnTheme.destructive,
+                  ),
+                  const SizedBox(width: ShadcnTheme.spacing2),
+                  Expanded(
+                    child: Text(
+                      controller.errorMessage!,
+                      style: ShadcnTheme.bodyMedium.copyWith(
+                        color: ShadcnTheme.destructive,
+                      ),
+                    ),
+                  ),
+                ],
+              ),
+            ),
 
           // 로그인 버튼
           ShadcnButton(
@@ -253,7 +267,7 @@ class _LoginViewRedesignState extends State<LoginViewRedesign>
             textColor: Colors.white,
             size: ShadcnButtonSize.large,
             fullWidth: true,
-            loading: _isLoading,
+            loading: controller.isLoading,
           ),
           const SizedBox(height: ShadcnTheme.spacing4),
 
@@ -261,8 +275,8 @@ class _LoginViewRedesignState extends State<LoginViewRedesign>
           ShadcnButton(
             text: '테스트 로그인',
             onPressed: () {
-              _usernameController.text = 'admin';
-              _passwordController.text = 'password';
+              controller.idController.text = 'admin@example.com';
+              controller.pwController.text = 'admin123';
               _handleLogin();
             },
             variant: ShadcnButtonVariant.secondary,