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>

docs/README_QUICKSTART.md

@@ -0,0 +1,94 @@
+# QQuiz Quick Start Guide
+
+## Step 1: Configure (30 seconds)
+
+Double-click to run:
+```
+setup.bat
+```
+
+This will:
+- Create `.env` file
+- Open it in Notepad
+- You need to replace `sk-your-openai-api-key-here` with your real OpenAI API key
+
+**Where to get API key:**
+- Visit: https://platform.openai.com/api-keys
+- Create new secret key
+- Copy and paste into `.env` file
+
+## Step 2: Start Application (3-5 minutes)
+
+Double-click to run:
+```
+start_app.bat
+```
+
+**PostgreSQL Password:**
+- When prompted, enter your PostgreSQL password
+- Default is usually: `postgres`
+- Or just press Enter to try without password
+
+The script will automatically:
+- ✓ Check Python and Node.js
+- ✓ Create database
+- ✓ Install all dependencies
+- ✓ Start backend (new window)
+- ✓ Start frontend (new window)
+
+## Step 3: Access System
+
+Browser will open automatically: http://localhost:3000
+
+**Login:**
+- Username: `admin`
+- Password: `admin123`
+
+**Test the system:**
+1. Click "题库管理" (Exam Management)
+2. Click "创建题库" (Create Exam)
+3. Enter name: `Test Exam`
+4. Upload file: `test_data/sample_questions.txt`
+5. Wait 10-30 seconds for AI to process
+6. Click "开始刷题" (Start Quiz)
+
+## What You'll See
+
+✅ Beautiful login page
+✅ Dashboard with statistics
+✅ Create exam and upload documents
+✅ AI processes questions automatically
+✅ Quiz player with different question types
+✅ Automatic mistake collection
+✅ Progress tracking
+
+## Troubleshooting
+
+### Can't find PostgreSQL password
+- Try: `postgres` or leave empty
+- Or check PostgreSQL installation
+
+### Port already in use
+```cmd
+netstat -ano | findstr :3000
+taskkill /F /PID <PID>
+```
+
+### Dependencies install failed
+- Check internet connection
+- Script uses China mirrors for speed
+
+## Success!
+
+If you see the login page at http://localhost:3000 - congratulations! 🎉
+
+The system is now running. You can:
+- Create exam banks
+- Upload documents (TXT/PDF/DOCX/XLSX)
+- Start quizzing
+- Review mistakes
+- Track progress
+
+---
+
+Enjoy using QQuiz! 🚀