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/model/user.go

@@ -0,0 +1,50 @@
+package model
+
+import (
+	"time"
+)
+
+// PermissionLevel 权限级别
+type PermissionLevel int
+
+const (
+	PermissionRead PermissionLevel = iota + 1
+	PermissionWrite
+	PermissionExecute
+	PermissionAdmin
+)
+
+// Role 角色
+type Role struct {
+	ID          string           `json:"id" gorm:"primaryKey"`
+	Name        string           `json:"name" gorm:"uniqueIndex"`
+	Permissions []PermissionLevel `json:"permissions" gorm:"type:int[]"`
+	CreatedAt   time.Time        `json:"created_at"`
+	UpdatedAt   time.Time        `json:"updated_at"`
+}
+
+// User 用户
+type User struct {
+	ID        string    `json:"id" gorm:"primaryKey"`
+	Username  string    `json:"username" gorm:"uniqueIndex;size:50;not null"`
+	Password  string    `json:"-" gorm:"not null"`
+	Email     string    `json:"email" gorm:"index"`
+	RoleID    string    `json:"role_id" gorm:"size:50;not null"`
+	Role      *Role    `json:"role,omitempty" gorm:"foreignKey:RoleID"`
+	IsActive  bool      `json:"is_active" gorm:"default:true"`
+	CreatedAt time.Time `json:"created_at"`
+	UpdatedAt time.Time `json:"updated_at"`
+}
+
+// HasPermission 检查是否有权限
+func (u *User) HasPermission(level PermissionLevel) bool {
+	if u.Role == nil {
+		return false
+	}
+	for _, p := range u.Role.Permissions {
+		if p >= level {
+			return true
+		}
+	}
+	return false
+}