add auth

lib/features/auth/data/datasources/auth_local_datasource.dart

@@ -20,6 +20,7 @@ class AuthLocalDataSource {
   static const String _fullNameKey = 'auth_session_full_name';
   static const String _createdAtKey = 'auth_session_created_at';
   static const String _appsKey = 'auth_session_apps';
+  static const String _rememberMeKey = 'auth_remember_me';
 
   AuthLocalDataSource(this._secureStorage);
 
@@ -102,21 +103,46 @@ class AuthLocalDataSource {
     return sid != null && csrfToken != null;
   }
 
+  /// Save "Remember Me" preference
+  ///
+  /// If true, user session will be restored on next app launch.
+  Future<void> saveRememberMe(bool rememberMe) async {
+    await _secureStorage.write(
+      key: _rememberMeKey,
+      value: rememberMe.toString(),
+    );
+  }
+
+  /// Get "Remember Me" preference
+  ///
+  /// Returns true if user wants to be remembered, false otherwise.
+  Future<bool> getRememberMe() async {
+    final value = await _secureStorage.read(key: _rememberMeKey);
+    return value == 'true';
+  }
+
   /// Clear session data
   ///
-  /// Called during logout to remove all session information.
+  /// Called during logout to remove all session information including rememberMe.
   Future<void> clearSession() async {
+    // Clear all session data including rememberMe
     await _secureStorage.delete(key: _sidKey);
     await _secureStorage.delete(key: _csrfTokenKey);
     await _secureStorage.delete(key: _fullNameKey);
     await _secureStorage.delete(key: _createdAtKey);
     await _secureStorage.delete(key: _appsKey);
+    await _secureStorage.delete(key: _rememberMeKey);
   }
 
-  /// Clear all authentication data
+  /// Clear all authentication data including remember me
   ///
   /// Complete cleanup of all stored auth data.
   Future<void> clearAll() async {
-    await _secureStorage.deleteAll();
+    await _secureStorage.delete(key: _sidKey);
+    await _secureStorage.delete(key: _csrfTokenKey);
+    await _secureStorage.delete(key: _fullNameKey);
+    await _secureStorage.delete(key: _createdAtKey);
+    await _secureStorage.delete(key: _appsKey);
+    await _secureStorage.delete(key: _rememberMeKey);
   }
 }

lib/features/auth/data/datasources/auth_remote_datasource.dart

@@ -56,6 +56,64 @@ class AuthRemoteDataSource {
     }
   }
 
+  /// Login
+  ///
+  /// Authenticates user with phone number.
+  /// Requires existing session (CSRF token and Cookie).
+  /// Returns new session with user credentials.
+  ///
+  /// API: POST /api/method/building_material.building_material.api.auth.login
+  /// Body: { "username": "phone", "googleid": null, "facebookid": null, "zaloid": null }
+  ///
+  /// Response includes new sid and csrf_token for authenticated user.
+  Future<GetSessionResponse> login({
+    required String phone,
+    required String csrfToken,
+    required String sid,
+    String? password, // Reserved for future use
+  }) async {
+    try {
+      final response = await _dio.post<Map<String, dynamic>>(
+        '/api/method/building_material.building_material.api.auth.login',
+        data: {
+          'username': phone,
+          'googleid': null,
+          'facebookid': null,
+          'zaloid': null,
+          // Password field reserved for future use
+          // 'password': password,
+        },
+        options: Options(
+          headers: {
+            'X-Frappe-Csrf-Token': csrfToken,
+            'Cookie': 'sid=$sid',
+            'Content-Type': 'application/json',
+          },
+        ),
+      );
+
+      if (response.statusCode == 200 && response.data != null) {
+        return GetSessionResponse.fromJson(response.data!);
+      } else {
+        throw ServerException(
+          'Login failed: ${response.statusCode}',
+        );
+      }
+    } on DioException catch (e) {
+      if (e.response?.statusCode == 401) {
+        throw const UnauthorizedException('Invalid credentials');
+      } else if (e.response?.statusCode == 404) {
+        throw NotFoundException('Login endpoint not found');
+      } else {
+        throw NetworkException(
+          e.message ?? 'Failed to login',
+        );
+      }
+    } catch (e) {
+      throw ServerException('Unexpected error during login: $e');
+    }
+  }
+
   /// Get Cities
   ///
   /// Fetches list of cities/provinces for address selection.