feat: 实现数据库驱动的API配置管理和项目结构重组

## 新功能
- 实现管理后台API配置管理（OpenAI/Anthropic/Qwen）
- API配置保存到数据库，实时生效无需重启
- API密钥遮罩显示（前10位+后4位）
- 完整endpoint URL自动显示

## 后端改进
- 新增 config_service.py 用于加载数据库配置
- LLMService 支持动态配置注入，回退到环境变量
- 更新 exam.py 和 question.py 使用数据库配置
- 扩展 schemas.py 支持所有API配置字段

## 前端改进
- 重写 AdminSettings.jsx 增强UI体验
- API密钥显示/隐藏切换
- 当前使用的提供商可视化标识
- 移除"需要重启"的误导性提示

## 项目结构重组
- 移动所有脚本到 scripts/ 目录
- 移动所有文档到 docs/ 目录
- 清理 Python 缓存文件

🤖 Generated with Claude Code

Co-Authored-By: Claude <noreply@anthropic.com>

scripts/check_status.bat

@@ -0,0 +1,89 @@
+@echo off
+title QQuiz - System Status Check
+
+cd /d "%~dp0.."
+
+echo.
+echo ========================================
+echo   QQuiz System Status Check
+echo ========================================
+echo.
+
+echo [1] Checking Python...
+python --version
+if %errorlevel% neq 0 (
+    echo ERROR: Python not found!
+) else (
+    echo OK
+)
+echo.
+
+echo [2] Checking Node.js...
+node --version
+if %errorlevel% neq 0 (
+    echo ERROR: Node.js not found!
+) else (
+    echo OK
+)
+echo.
+
+echo [3] Checking PostgreSQL...
+psql --version
+if %errorlevel% neq 0 (
+    echo WARNING: PostgreSQL command not found in PATH
+) else (
+    echo OK
+)
+echo.
+
+echo [4] Checking if backend is running...
+curl -s http://localhost:8000/health >nul 2>&1
+if %errorlevel% neq 0 (
+    echo ERROR: Backend is NOT running on port 8000
+    echo.
+    echo Backend must be started first!
+    echo Run the backend window manually:
+    echo   cd backend
+    echo   venv\Scripts\activate.bat
+    echo   uvicorn main:app --reload
+) else (
+    echo OK - Backend is running
+)
+echo.
+
+echo [5] Checking if frontend is running...
+curl -s http://localhost:3000 >nul 2>&1
+if %errorlevel% neq 0 (
+    echo WARNING: Frontend is NOT running on port 3000
+) else (
+    echo OK - Frontend is running
+)
+echo.
+
+echo [6] Checking ports...
+echo Checking port 8000 (Backend):
+netstat -ano | findstr :8000
+echo.
+echo Checking port 3000 (Frontend):
+netstat -ano | findstr :3000
+echo.
+
+echo [7] Checking .env configuration...
+if exist ".env" (
+    echo OK - .env file exists
+    findstr /C:"OPENAI_API_KEY=sk-" .env >nul
+    if %errorlevel% neq 0 (
+        echo WARNING: OPENAI_API_KEY may not be configured properly
+    ) else (
+        echo OK - API Key appears to be configured
+    )
+) else (
+    echo ERROR: .env file not found!
+)
+echo.
+
+echo ========================================
+echo   Diagnosis Complete
+echo ========================================
+echo.
+pause