이메일/비밀번호 로그인 기능 구현

frontend/lib/core/services/auth_proxy_service.dart

@@ -66,6 +66,26 @@ class AuthProxyService {
     }
   }
 
+  static Future<Map<String, dynamic>> loginWithPassword(String loginId, String password) async {
+    final url = Uri.parse('$_baseUrl/api/v1/auth/password/login');
+    
+    final response = await http.post(
+      url,
+      headers: {'Content-Type': 'application/json'},
+      body: jsonEncode({
+        'loginId': loginId,
+        'password': password,
+      }),
+    );
+
+    if (response.statusCode == 200) {
+      return jsonDecode(response.body);
+    } else {
+      final errorBody = jsonDecode(response.body);
+      throw Exception(errorBody['error'] ?? 'Failed to login');
+    }
+  }
+
   static Future<void> sendSms(String phoneNumber) async {
     final url = Uri.parse('$_baseUrl/api/v1/auth/sms');