feat(server): 实现统一响应格式和错误码

- 添加 server/go.mod，模块路径为 github.com/1024XEngineer/xinfra/server
- 实现 response.go 统一 JSON 响应结构：
  - 响应信封：{ code, message, data, details }
  - 业务错误码 (10001-20002) 与 MVP 规范一致
  - 便捷函数：Success, Error, BadRequest, Unauthorized 等
  - 分页响应支持，包含 total 和 items
- 添加 recovery 中间件捕获 panic 并返回 500 错误
- 添加 logger 中间件记录请求日志

为所有后端处理器建立统一的 API 响应基础，与前端期望的格式保持一致。

server/internal/handler/response.go

@@ -0,0 +1,143 @@
+package handler
+
+import (
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+)
+
+// Response 统一响应结构
+type Response struct {
+	Code    int         `json:"code"`             // 业务错误码，0 表示成功
+	Message string      `json:"message"`          // 响应消息
+	Data    interface{} `json:"data,omitempty"`    // 响应数据，成功时返回
+	Details string      `json:"details,omitempty"` // 错误详情，失败时返回
+}
+
+// 分页响应结构
+type PaginatedData struct {
+	Total int64       `json:"total"`
+	Items interface{} `json:"items"`
+}
+
+// 业务错误码定义
+const (
+	// 成功
+	CodeSuccess = 0
+
+	// 认证相关错误 10001-10099
+	CodeLDAPAuthFailed     = 10001 // LDAP 认证失败
+	CodeInvalidCredentials = 10002 // 用户名或密码错误
+	CodeTokenExpired       = 10003 // Token 已过期
+	CodeSSONotConfigured   = 10004 // 子系统未配置 SSO
+	CodeSSOGenerateFailed  = 10005 // SSO 跳转生成失败
+
+	// 任务相关错误 20001-20099
+	CodeTaskCreateFailed  = 20001 // Ansible 任务创建失败
+	CodeTaskExecTimeout   = 20002 // Ansible 任务执行超时
+)
+
+// 错误码对应的默认消息
+var codeMessages = map[int]string{
+	CodeSuccess:            "success",
+	CodeLDAPAuthFailed:     "LDAP 认证失败",
+	CodeInvalidCredentials: "用户名或密码错误",
+	CodeTokenExpired:       "Token 已过期",
+	CodeSSONotConfigured:   "子系统未配置 SSO",
+	CodeSSOGenerateFailed:  "SSO 跳转生成失败",
+	CodeTaskCreateFailed:   "Ansible 任务创建失败",
+	CodeTaskExecTimeout:    "Ansible 任务执行超时",
+}
+
+// GetMessage 根据错误码获取默认消息
+func GetMessage(code int) string {
+	if msg, ok := codeMessages[code]; ok {
+		return msg
+	}
+	return "未知错误"
+}
+
+// Success 返回成功响应
+func Success(c *gin.Context, data interface{}) {
+	c.JSON(http.StatusOK, Response{
+		Code:    CodeSuccess,
+		Message: GetMessage(CodeSuccess),
+		Data:    data,
+	})
+}
+
+// SuccessWithMessage 返回自定义消息的成功响应
+func SuccessWithMessage(c *gin.Context, message string, data interface{}) {
+	c.JSON(http.StatusOK, Response{
+		Code:    CodeSuccess,
+		Message: message,
+		Data:    data,
+	})
+}
+
+// SuccessWithPaginated 返回分页成功响应
+func SuccessWithPaginated(c *gin.Context, total int64, items interface{}) {
+	c.JSON(http.StatusOK, Response{
+		Code:    CodeSuccess,
+		Message: GetMessage(CodeSuccess),
+		Data: PaginatedData{
+			Total: total,
+			Items: items,
+		},
+	})
+}
+
+// Error 返回错误响应
+func Error(c *gin.Context, httpCode int, bizCode int, details string) {
+	c.JSON(httpCode, Response{
+		Code:    bizCode,
+		Message: GetMessage(bizCode),
+		Details: details,
+	})
+}
+
+// ErrorWithMessage 返回自定义消息的错误响应
+func ErrorWithMessage(c *gin.Context, httpCode int, bizCode int, message string, details string) {
+	c.JSON(httpCode, Response{
+		Code:    bizCode,
+		Message: message,
+		Details: details,
+	})
+}
+
+// BadRequest 返回 400 错误
+func BadRequest(c *gin.Context, details string) {
+	Error(c, http.StatusBadRequest, CodeInvalidCredentials, details)
+}
+
+// Unauthorized 返回 401 错误
+func Unauthorized(c *gin.Context, details string) {
+	Error(c, http.StatusUnauthorized, CodeTokenExpired, details)
+}
+
+// Forbidden 返回 403 错误
+func Forbidden(c *gin.Context, details string) {
+	c.JSON(http.StatusForbidden, Response{
+		Code:    http.StatusForbidden,
+		Message: "无权限访问",
+		Details: details,
+	})
+}
+
+// NotFound 返回 404 错误
+func NotFound(c *gin.Context, details string) {
+	c.JSON(http.StatusNotFound, Response{
+		Code:    http.StatusNotFound,
+		Message: "资源不存在",
+		Details: details,
+	})
+}
+
+// InternalError 返回 500 错误
+func InternalError(c *gin.Context, details string) {
+	c.JSON(http.StatusInternalServerError, Response{
+		Code:    http.StatusInternalServerError,
+		Message: "服务器内部错误",
+		Details: details,
+	})
+}