feat: 重构前后端架构，添加Go后端和Python Agent服务

- 新增 Go 语言后端服务(server/)，包含用户认证、Agent管理、数据库连接等API
- 新增 Python Agent 服务(agent/)，实现Agent核心逻辑和工具集
- 前端从原生HTML迁移到Vue.js框架(web/src/)
- 添加 Docker Compose 支持(docker-compose.yml)
- 添加项目架构文档(docs/ARCHITECTURE.md)
- 添加环境变量示例(.env.example)和本地启动脚本(start-local.ps1)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/internal/middleware/auth.go

@@ -0,0 +1,71 @@
+package middleware
+
+import (
+	"net/http"
+	"strings"
+
+	"x-agents/server/internal/service"
+
+	"github.com/gin-gonic/gin"
+)
+
+// CORS 中间件
+func CORS() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		c.Header("Access-Control-Allow-Origin", "*")
+		c.Header("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS")
+		c.Header("Access-Control-Allow-Headers", "Origin, Content-Type, Authorization")
+		c.Header("Access-Control-Max-Age", "86400")
+
+		if c.Request.Method == "OPTIONS" {
+			c.AbortWithStatus(http.StatusNoContent)
+			return
+		}
+
+		c.Next()
+	}
+}
+
+// Recovery 中间件 - 恢复 panic
+func Recovery() gin.HandlerFunc {
+	return gin.Recovery()
+}
+
+// Auth 认证中间件
+func Auth(jwtSecret string) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		// 从 Header 获取 Token
+		authHeader := c.GetHeader("Authorization")
+		if authHeader == "" {
+			c.JSON(http.StatusUnauthorized, gin.H{"error": "authorization header required"})
+			c.Abort()
+			return
+		}
+
+		// 解析 Bearer Token
+		parts := strings.SplitN(authHeader, " ", 2)
+		if len(parts) != 2 || parts[0] != "Bearer" {
+			c.JSON(http.StatusUnauthorized, gin.H{"error": "invalid authorization format"})
+			c.Abort()
+			return
+		}
+
+		tokenString := parts[1]
+
+		// 验证 Token
+		authService := service.NewAuthService(jwtSecret, nil)
+		claims, err := authService.ValidateToken(tokenString)
+		if err != nil {
+			c.JSON(http.StatusUnauthorized, gin.H{"error": "invalid token"})
+			c.Abort()
+			return
+		}
+
+		// 将用户信息存入上下文
+		c.Set("user_id", claims["sub"])
+		c.Set("username", claims["username"])
+		c.Set("role", claims["role"])
+
+		c.Next()
+	}
+}