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/fix_and_start.bat

@@ -0,0 +1,140 @@
+@echo off
+title QQuiz - Fix and Start
+color 0E
+
+echo.
+echo ========================================
+echo   QQuiz - Automatic Fix and Start
+echo ========================================
+echo.
+
+cd /d "%~dp0.."
+
+REM Check if .env exists
+if not exist ".env" (
+    echo Creating .env file...
+    copy .env.example .env >nul
+    echo.
+    echo IMPORTANT: Edit .env and set your OPENAI_API_KEY
+    echo Opening .env file...
+    timeout /t 2 /nobreak >nul
+    notepad .env
+    echo.
+    echo Save and close .env, then press any key to continue...
+    pause >nul
+)
+
+echo.
+echo Choose database option:
+echo.
+echo [1] Use Docker (Recommended - Easy)
+echo [2] Use Local PostgreSQL (Advanced)
+echo.
+choice /C 12 /M "Select option"
+
+if %errorlevel% equ 1 (
+    echo.
+    echo Using Docker PostgreSQL...
+    echo.
+
+    REM Check Docker
+    docker --version >nul 2>&1
+    if %errorlevel% neq 0 (
+        echo ERROR: Docker not found!
+        echo.
+        echo Please install Docker Desktop:
+        echo https://www.docker.com/products/docker-desktop/
+        echo.
+        echo After installing Docker, run this script again.
+        pause
+        exit /b 1
+    )
+
+    echo Starting MySQL in Docker...
+    docker-compose up -d mysql
+
+    if %errorlevel% neq 0 (
+        echo.
+        echo Docker failed to start. Trying to fix...
+        docker-compose down
+        docker-compose up -d mysql
+    )
+
+    echo Waiting for database...
+    timeout /t 10 /nobreak >nul
+
+) else (
+    echo.
+    echo Using Local MySQL...
+    echo.
+    echo Make sure MySQL is running on port 3306
+    echo.
+    echo If you see connection errors, you need to:
+    echo 1. Start MySQL service
+    echo 2. Or install MySQL from https://dev.mysql.com/downloads/installer/
+    echo 3. Or choose option 1 to use Docker instead
+    echo.
+    pause
+)
+
+echo.
+echo ========================================
+echo   Starting Backend...
+echo ========================================
+echo.
+
+cd backend
+
+if not exist "venv\Scripts\activate.bat" (
+    echo Creating virtual environment...
+    python -m venv venv
+)
+
+echo Installing dependencies...
+call venv\Scripts\activate.bat
+pip install -q -r requirements.txt -i https://pypi.tuna.tsinghua.edu.cn/simple
+
+echo.
+echo Running database migrations...
+alembic upgrade head
+
+if %errorlevel% neq 0 (
+    echo.
+    echo WARNING: Database migration failed
+    echo The app will try to create tables automatically
+    echo.
+)
+
+cd ..
+
+echo.
+echo Starting services...
+echo.
+
+start "QQuiz Backend" cmd /k "cd /d %~dp0..backend && call venv\Scripts\activate.bat && echo Backend: http://localhost:8000 && echo Docs: http://localhost:8000/docs && echo. && uvicorn main:app --reload"
+
+timeout /t 8 /nobreak >nul
+
+start "QQuiz Frontend" cmd /k "cd /d %~dp0..frontend && echo Frontend: 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.
+echo Login: admin / admin123
+echo.
+echo ========================================
+echo.
+
+timeout /t 5 /nobreak >nul
+start http://localhost:3000
+
+echo.
+echo System is running...
+echo Close backend/frontend windows to stop
+echo.
+pause