feat(backend): Day 5 - backend basic architecture setup completed

backend/src/config/database.ts

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+import { PrismaClient } from '@prisma/client';
+
+// 创建Prisma Client实例
+export const prisma = new PrismaClient({
+  log: process.env.NODE_ENV === 'development' ? ['query', 'info', 'warn', 'error'] : ['error'],
+});
+
+// 数据库连接测试
+export async function testDatabaseConnection(): Promise<boolean> {
+  try {
+    await prisma.$connect();
+    console.log('✅ 数据库连接成功！');
+    
+    // 获取数据库信息
+    const result = await prisma.$queryRaw<Array<{ version: string }>>`SELECT version()`;
+    console.log('📊 数据库版本:', result[0]?.version.split(' ')[0], result[0]?.version.split(' ')[1]);
+    
+    return true;
+  } catch (error) {
+    console.error('❌ 数据库连接失败:', error);
+    return false;
+  }
+}
+
+// 优雅关闭数据库连接
+export async function closeDatabaseConnection() {
+  await prisma.$disconnect();
+  console.log('👋 数据库连接已关闭');
+}
+
+// 进程退出时关闭连接
+process.on('beforeExit', async () => {
+  await closeDatabaseConnection();
+});
+

backend/src/config/env.ts

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+import { config as dotenvConfig } from 'dotenv';
+
+dotenvConfig();
+
+export const config = {
+  // 服务器配置
+  nodeEnv: process.env.NODE_ENV || 'development',
+  port: parseInt(process.env.PORT || '3001', 10),
+  host: process.env.HOST || '0.0.0.0',
+
+  // 数据库配置
+  databaseUrl: process.env.DATABASE_URL || '',
+
+  // Redis配置
+  redisUrl: process.env.REDIS_URL || 'redis://localhost:6379',
+
+  // JWT配置
+  jwtSecret: process.env.JWT_SECRET || 'your-secret-key',
+
+  // 大模型API Keys
+  deepseekApiKey: process.env.DEEPSEEK_API_KEY || '',
+  qwenApiKey: process.env.QWEN_API_KEY || '',
+  geminiApiKey: process.env.GEMINI_API_KEY || '',
+
+  // Dify配置
+  difyApiUrl: process.env.DIFY_API_URL || 'http://localhost:5001',
+  difyApiKey: process.env.DIFY_API_KEY || '',
+
+  // 文件上传配置
+  uploadMaxSize: parseInt(process.env.UPLOAD_MAX_SIZE || '10485760', 10),
+  uploadDir: process.env.UPLOAD_DIR || './uploads',
+
+  // 日志配置
+  logLevel: process.env.LOG_LEVEL || 'info',
+};
+

backend/src/index.ts

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+import Fastify from 'fastify';
+import cors from '@fastify/cors';
+import { config } from './config/env.js';
+import { testDatabaseConnection, prisma } from './config/database.js';
+
+const fastify = Fastify({
+  logger: {
+    level: config.logLevel,
+    transport: {
+      target: 'pino-pretty',
+      options: {
+        colorize: true,
+        translateTime: 'HH:MM:ss Z',
+        ignore: 'pid,hostname',
+      },
+    },
+  },
+});
+
+// 注册CORS插件
+await fastify.register(cors, {
+  origin: true, // 开发环境允许所有来源
+  credentials: true,
+});
+
+// 健康检查路由
+fastify.get('/health', async () => {
+  // 检查数据库连接
+  let dbStatus = 'unknown';
+  try {
+    await prisma.$queryRaw`SELECT 1`;
+    dbStatus = 'connected';
+  } catch {
+    dbStatus = 'disconnected';
+  }
+
+  return {
+    status: 'ok',
+    database: dbStatus,
+    timestamp: new Date().toISOString(),
+    uptime: process.uptime(),
+  };
+});
+
+// API路由前缀
+fastify.get('/api/v1', async () => {
+  return {
+    message: 'AI Clinical Research Platform API',
+    version: '1.0.0',
+    environment: config.nodeEnv,
+  };
+});
+
+// 启动服务器
+const start = async () => {
+  try {
+    // 测试数据库连接
+    console.log('🔍 正在测试数据库连接...');
+    const dbConnected = await testDatabaseConnection();
+    
+    if (!dbConnected) {
+      console.error('❌ 数据库连接失败，无法启动服务器');
+      process.exit(1);
+    }
+
+    // 启动Fastify服务器
+    await fastify.listen({
+      port: config.port,
+      host: config.host,
+    });
+    
+    console.log('\n' + '='.repeat(60));
+    console.log('🚀 AI临床研究平台 - 后端服务器启动成功！');
+    console.log('='.repeat(60));
+    console.log(`📍 服务地址: http://${config.host === '0.0.0.0' ? 'localhost' : config.host}:${config.port}`);
+    console.log(`🔍 健康检查: http://localhost:${config.port}/health`);
+    console.log(`📡 API入口: http://localhost:${config.port}/api/v1`);
+    console.log(`🌍 运行环境: ${config.nodeEnv}`);
+    console.log('='.repeat(60) + '\n');
+  } catch (err) {
+    fastify.log.error(err);
+    process.exit(1);
+  }
+};
+
+start();
+