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/run_local.sh

@@ -0,0 +1,88 @@
+#!/bin/bash
+
+set -e
+
+echo "===== QQuiz Local Deployment Script ====="
+
+# Check if .env exists
+if [ ! -f .env ]; then
+    echo "Error: .env file not found!"
+    echo "Please copy .env.example to .env and configure it."
+    exit 1
+fi
+
+# Load environment variables
+export $(grep -v '^#' .env | xargs)
+
+# Check Python version
+PYTHON_VERSION=$(python3 --version 2>&1 | awk '{print $2}')
+echo "Python version: $PYTHON_VERSION"
+
+# Check if PostgreSQL is running
+echo "Checking PostgreSQL connection..."
+if ! pg_isready -h localhost -p 5432 &> /dev/null; then
+    echo "Warning: PostgreSQL is not running on localhost:5432"
+    echo "Please start PostgreSQL or use Docker: docker-compose up -d postgres"
+    read -p "Continue anyway? (y/n) " -n 1 -r
+    echo
+    if [[ ! $REPLY =~ ^[Yy]$ ]]; then
+        exit 1
+    fi
+fi
+
+# Install backend dependencies
+echo "Installing backend dependencies..."
+cd backend
+if [ ! -d "venv" ]; then
+    echo "Creating virtual environment..."
+    python3 -m venv venv
+fi
+
+source venv/bin/activate
+pip install -r requirements.txt
+
+# Run database migrations
+echo "Running database migrations..."
+alembic upgrade head || echo "Warning: Alembic migration failed. Database might not be initialized."
+
+# Create uploads directory
+mkdir -p uploads
+
+# Start backend
+echo "Starting backend on http://localhost:8000..."
+uvicorn main:app --host 0.0.0.0 --port 8000 --reload &
+BACKEND_PID=$!
+
+cd ../frontend
+
+# Install frontend dependencies
+echo "Installing frontend dependencies..."
+if [ ! -d "node_modules" ]; then
+    npm install
+fi
+
+# Start frontend
+echo "Starting frontend on http://localhost:3000..."
+npm start &
+FRONTEND_PID=$!
+
+echo ""
+echo "===== QQuiz is running! ====="
+echo "Backend:  http://localhost:8000"
+echo "Frontend: http://localhost:3000"
+echo "API Docs: http://localhost:8000/docs"
+echo ""
+echo "Press Ctrl+C to stop all services"
+
+# Handle cleanup on exit
+cleanup() {
+    echo ""
+    echo "Stopping services..."
+    kill $BACKEND_PID $FRONTEND_PID 2>/dev/null
+    exit 0
+}
+
+trap cleanup SIGINT SIGTERM
+
+# Wait for processes
+wait