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/repository/user_repo.go

@@ -0,0 +1,66 @@
+package repository
+
+import (
+	"x-agents/server/internal/model"
+
+	"gorm.io/gorm"
+)
+
+type UserRepository struct {
+	db *gorm.DB
+}
+
+func NewUserRepository(db *gorm.DB) *UserRepository {
+	return &UserRepository{db: db}
+}
+
+func (r *UserRepository) Create(user *model.User) error {
+	return r.db.Create(user).Error
+}
+
+func (r *UserRepository) FindByID(id string) (*model.User, error) {
+	var user model.User
+	err := r.db.Preload("Role").First(&user, "id = ?", id).Error
+	if err != nil {
+		return nil, err
+	}
+	return &user, nil
+}
+
+func (r *UserRepository) FindByUsername(username string) (*model.User, error) {
+	var user model.User
+	err := r.db.Preload("Role").First(&user, "username = ?", username).Error
+	if err != nil {
+		return nil, err
+	}
+	return &user, nil
+}
+
+func (r *UserRepository) FindAll() ([]model.User, error) {
+	var users []model.User
+	err := r.db.Preload("Role").Find(&users).Error
+	return users, err
+}
+
+func (r *UserRepository) Update(user *model.User) error {
+	return r.db.Save(user).Error
+}
+
+func (r *UserRepository) Delete(id string) error {
+	return r.db.Delete(&model.User{}, "id = ?", id).Error
+}
+
+// FindRoleByID 根据ID查找角色
+func (r *UserRepository) FindRoleByID(id string) (*model.Role, error) {
+	var role model.Role
+	err := r.db.First(&role, "id = ?", id).Error
+	if err != nil {
+		return nil, err
+	}
+	return &role, nil
+}
+
+// CreateRole 创建角色
+func (r *UserRepository) CreateRole(role *model.Role) error {
+	return r.db.Create(role).Error
+}