fix: resolve double data unwrapping issue in API calls

Issue: projectApi and agentApi were unwrapping response.data twice:
1. request interceptor returns response.data
2. API functions returned response.data again (undefined)

This caused all API calls to fail silently with 'response.success' being undefined.

Fixed:
- projectApi: Removed redundant .data access
- agentApi: Removed redundant .data access

All API functions now correctly return the backend response:
{ success: true, data: [...] }

This fixes:
- '鑾峰彇椤圭洰鍒楄〃澶辫触' error on page load
- '鍒涘缓椤圭洰澶辫触' error when creating projects
- Any other API call failures

测试API.bat

@@ -0,0 +1,89 @@
+@echo off
+chcp 65001 >nul
+echo ========================================
+echo   API测试工具
+echo ========================================
+echo.
+
+echo [测试1] 后端健康检查
+echo URL: http://localhost:3001/health
+curl -s http://localhost:3001/health
+if errorlevel 1 (
+    echo.
+    echo ❌ 后端服务未响应
+    echo    解决方案: cd backend ^&^& npm run dev
+    goto :end
+) else (
+    echo.
+    echo ✅ 后端服务正常
+)
+echo.
+echo ----------------------------------------
+echo.
+
+echo [测试2] 获取项目列表
+echo URL: http://localhost:3001/api/v1/projects
+curl -s http://localhost:3001/api/v1/projects
+if errorlevel 1 (
+    echo.
+    echo ❌ 获取项目列表失败
+) else (
+    echo.
+    echo ✅ 获取项目列表成功
+)
+echo.
+echo ----------------------------------------
+echo.
+
+echo [测试3] 获取智能体列表
+echo URL: http://localhost:3001/api/v1/agents
+curl -s http://localhost:3001/api/v1/agents
+if errorlevel 1 (
+    echo.
+    echo ❌ 获取智能体列表失败
+) else (
+    echo.
+    echo ✅ 获取智能体列表成功
+)
+echo.
+echo ----------------------------------------
+echo.
+
+echo [测试4] 创建测试项目
+echo URL: http://localhost:3001/api/v1/projects
+echo 正在创建项目...
+curl -X POST http://localhost:3001/api/v1/projects -H "Content-Type: application/json" -d "{\"name\":\"API测试项目\",\"background\":\"这是通过脚本创建的测试项目\",\"researchType\":\"observational\"}"
+if errorlevel 1 (
+    echo.
+    echo ❌ 创建项目失败
+) else (
+    echo.
+    echo ✅ 创建项目成功
+)
+echo.
+echo ----------------------------------------
+echo.
+
+echo [测试5] 前端服务检查
+echo URL: http://localhost:3000
+curl -s http://localhost:3000 >nul 2>&1
+if errorlevel 1 (
+    echo ❌ 前端服务未响应
+    echo    解决方案: cd frontend ^&^& npm run dev
+) else (
+    echo ✅ 前端服务正常
+)
+echo.
+
+:end
+echo ========================================
+echo   测试完成
+echo ========================================
+echo.
+echo 如果所有测试都通过，但浏览器仍有问题：
+echo 1. 按 Ctrl + Shift + R 强制刷新浏览器
+echo 2. 查看浏览器控制台（F12）的错误信息
+echo 3. 查看解决方案-前端获取数据失败.md
+echo.
+pause
+