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/start_with_docker_db.bat

@@ -0,0 +1,74 @@
+@echo off
+title QQuiz - Start with Docker Database
+color 0B
+
+echo.
+echo ========================================
+echo   QQuiz - Starting with Docker DB
+echo ========================================
+echo.
+
+cd /d "%~dp0.."
+
+echo [1/4] Checking Docker...
+docker --version >nul 2>&1
+if %errorlevel% neq 0 (
+    echo ERROR: Docker not found!
+    echo Please install Docker Desktop from https://www.docker.com/
+    pause
+    exit /b 1
+)
+echo OK - Docker installed
+echo.
+
+echo [2/4] Starting MySQL in Docker...
+docker-compose up -d mysql
+
+if %errorlevel% neq 0 (
+    echo ERROR: Failed to start MySQL
+    echo Try: docker-compose down
+    echo Then run this script again
+    pause
+    exit /b 1
+)
+
+echo OK - MySQL started
+echo Waiting for database to be ready...
+echo.
+timeout /t 10 /nobreak >nul
+echo.
+
+echo [3/4] Starting Backend...
+start "QQuiz Backend" cmd /k "cd /d %~dp0..backend && call venv\Scripts\activate.bat && echo ======================================== && echo   QQuiz Backend Server && echo ======================================== && echo. && echo API: http://localhost:8000 && echo Docs: http://localhost:8000/docs && echo. && alembic upgrade head && echo. && uvicorn main:app --reload"
+
+echo Waiting for backend to start...
+timeout /t 8 /nobreak >nul
+echo.
+
+echo [4/4] Starting Frontend...
+start "QQuiz Frontend" cmd /k "cd /d %~dp0..frontend && echo ======================================== && echo   QQuiz Frontend Server && echo ======================================== && echo. && echo URL: http://localhost:3000 && echo. && npm start"
+
+echo.
+echo ========================================
+echo   SUCCESS! QQuiz is starting...
+echo ========================================
+echo.
+echo Frontend: http://localhost:3000
+echo Backend:  http://localhost:8000
+echo Database: Running in Docker
+echo.
+echo Login:
+echo   Username: admin
+echo   Password: admin123
+echo.
+echo ========================================
+echo.
+
+timeout /t 5 /nobreak >nul
+start http://localhost:3000
+
+echo System running...
+echo To stop: Close the backend/frontend windows
+echo To stop database: docker-compose down
+echo.
+pause