[阶段1.1-1.7] 实现完整的认证系统

后端实现:
- 创建 AuthService 包含密码加密、JWT 生成和验证
- 创建 authMiddleware 用于 API 路由保护
- 实现 auth 路由 (register, login, logout, /me)

前端实现:
- 创建 Login 页面 (登录/注册标签页)
- 创建 ProtectedRoute 组件用于路由保护
- 更新 App.tsx 集成路由保护
- 前端 API 客户端已包含认证方法和拦截器

验收标准已满足:
- 用户可以注册和登录
- JWT Token 正确生成和验证
- 受保护的路由需要有效 Token
- 未认证用户重定向到登录页面

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

server/src/middleware/authMiddleware.ts

@@ -0,0 +1,65 @@
+import { Request, Response, NextFunction } from 'express';
+import { verifyToken } from '../services/AuthService';
+import { AppError } from './errorHandler';
+
+export interface AuthRequest extends Request {
+  userId?: string;
+  userEmail?: string;
+}
+
+export function authMiddleware(req: AuthRequest, res: Response, next: NextFunction) {
+  const authHeader = req.headers.authorization;
+
+  if (!authHeader) {
+    return res.status(401).json({
+      error: {
+        status: 401,
+        message: 'Missing authorization header',
+      },
+    });
+  }
+
+  const parts = authHeader.split(' ');
+  if (parts.length !== 2 || parts[0] !== 'Bearer') {
+    return res.status(401).json({
+      error: {
+        status: 401,
+        message: 'Invalid authorization header format',
+      },
+    });
+  }
+
+  const token = parts[1];
+
+  try {
+    const payload = verifyToken(token);
+    req.userId = payload.userId;
+    next();
+  } catch (error: any) {
+    return res.status(401).json({
+      error: {
+        status: 401,
+        message: 'Invalid or expired token',
+      },
+    });
+  }
+}
+
+export function optionalAuthMiddleware(req: AuthRequest, res: Response, next: NextFunction) {
+  const authHeader = req.headers.authorization;
+
+  if (authHeader) {
+    const parts = authHeader.split(' ');
+    if (parts.length === 2 && parts[0] === 'Bearer') {
+      const token = parts[1];
+      try {
+        const payload = verifyToken(token);
+        req.userId = payload.userId;
+      } catch (error) {
+        // Silently fail - continue without authentication
+      }
+    }
+  }
+
+  next();
+}