improvement: error handeling structure changed and unified all across the app. user no longer sees inappropriate messages.

frontend/src/lib/api/client.ts

@@ -88,13 +88,34 @@ apiClient.interceptors.response.use(
       }
     }
 
+    const responseData = error.response?.data as
+      | { success?: false; error?: { code?: string; statusCode?: number; details?: ApiError['details'] } }
+      | { message?: string | string[] }
+      | undefined;
+
+    if (responseData && 'error' in responseData && responseData.error?.code) {
+      const apiError: ApiError = {
+        statusCode: responseData.error.statusCode ?? error.response?.status ?? 500,
+        code: responseData.error.code,
+        details: responseData.error.details,
+      };
+      return Promise.reject(apiError);
+    }
+
     const apiError: ApiError = {
       statusCode: error.response?.status || 500,
-      message:
-        (error.response?.data as any)?.message ||
-        error.message ||
-        'An unexpected error occurred',
-      error: (error.response?.data as any)?.error,
+      code:
+        error.response?.status === 401
+          ? 'AUTH_UNAUTHORIZED'
+          : error.response?.status === 403
+            ? 'PERMISSION_DENIED'
+            : error.response?.status === 404
+              ? 'NOT_FOUND'
+              : error.response?.status === 409
+                ? 'CONFLICT'
+                : (error.response?.status ?? 500) >= 500
+                  ? 'INTERNAL_ERROR'
+                  : 'BAD_REQUEST',
     };
 
     return Promise.reject(apiError);