refactor: introduce Wire dependency injection and interface-based architecture

- Add Google Wire for compile-time dependency injection
- Replace concrete service types with interfaces across handlers
- Remove global state (DB, cache) in favor of constructor injection
- Split monolithic files into focused modules:
  - config: separate files for each config domain
  - dto: converters split by domain (user, post, message, group)
  - cache: separate metrics.go and redis_cache.go
- Introduce unified apperrors package with string-based error codes
- Add transaction support with context-aware repository methods
- Upgrade golang.org/x/crypto from 0.17.0 to 0.26.0

internal/pkg/response/response.go

@@ -5,7 +5,7 @@ import (
 
 	"github.com/gin-gonic/gin"
 
-	"carrot_bbs/internal/service"
+	apperrors "carrot_bbs/internal/errors"
 )
 
 // Response 统一响应结构
@@ -119,44 +119,72 @@ func Paginated(c *gin.Context, list interface{}, total int64, page, pageSize int
 }
 
 // HandleServiceError 统一处理 Service 错误
-// 如果 err 是 *service.ServiceError，返回对应的业务错误码和消息
+// 如果 err 是 *apperrors.AppError，返回对应的业务错误码和消息
 // 如果 err 是其他错误，返回 false（调用方应处理通用错误）
 // 返回 true 表示错误已处理，false 表示需要调用方继续处理
 func HandleServiceError(c *gin.Context, err error) bool {
 	if err == nil {
 		return false
 	}
-	if se, ok := err.(*service.ServiceError); ok {
-		ErrorWithStatusCode(c, statusCodeFromCode(se.Code), se.Code, se.Message)
+	if se, ok := apperrors.As(err); ok {
+		statusCode := statusCodeFromAppErrorCode(se.Code)
+		ErrorWithStringCode(c, statusCode, se.Code, se.Message)
 		return true
 	}
 	return false
 }
 
 // HandleError 统一处理错误（带默认消息）
-// 如果 err 是 *service.ServiceError，返回对应的业务错误码和消息
+// 如果 err 是 *apperrors.AppError，返回对应的业务错误码和消息
 // 如果 err 是其他错误，返回 InternalServerError 并使用 defaultMessage
 func HandleError(c *gin.Context, err error, defaultMessage string) {
 	if err == nil {
 		return
 	}
-	if se, ok := err.(*service.ServiceError); ok {
-		ErrorWithStatusCode(c, statusCodeFromCode(se.Code), se.Code, se.Message)
+	if se, ok := apperrors.As(err); ok {
+		statusCode := statusCodeFromAppErrorCode(se.Code)
+		ErrorWithStringCode(c, statusCode, se.Code, se.Message)
 		return
 	}
 	InternalServerError(c, defaultMessage)
 }
 
-// statusCodeFromCode 根据业务错误码获取 HTTP 状态码
-func statusCodeFromCode(code int) int {
-	switch {
-	case code >= 200 && code < 300:
-		return http.StatusOK
-	case code >= 400 && code < 500:
-		return code
-	case code >= 500:
-		return code
+// statusCodeFromAppErrorCode 根据AppError的错误码字符串获取 HTTP 状态码
+func statusCodeFromAppErrorCode(code string) int {
+	switch code {
+	case "NOT_FOUND", "USER_NOT_FOUND", "POST_NOT_FOUND", "GROUP_NOT_FOUND",
+		"GROUP_REQUEST_NOT_FOUND", "SCHEDULE_COURSE_NOT_FOUND":
+		return http.StatusNotFound
+	case "UNAUTHORIZED", "INVALID_CREDENTIALS":
+		return http.StatusUnauthorized
+	case "FORBIDDEN", "NOT_GROUP_MEMBER", "NOT_GROUP_ADMIN", "NOT_GROUP_OWNER",
+		"USER_BANNED", "USER_BLOCKED", "MUTED", "MUTE_ALL_ENABLED",
+		"SCHEDULE_FORBIDDEN", "UNAUTHORIZED_NOTIFICATION":
+		return http.StatusForbidden
+	case "BAD_REQUEST", "INVALID_USERNAME", "INVALID_EMAIL", "INVALID_PHONE",
+		"WEAK_PASSWORD", "USERNAME_EXISTS", "EMAIL_EXISTS", "PHONE_EXISTS",
+		"USER_ALREADY_EXISTS", "INVALID_OPERATION", "VERIFICATION_CODE_INVALID",
+		"VERIFICATION_CODE_EXPIRED", "EMAIL_ALREADY_VERIFIED", "EMAIL_NOT_BOUND",
+		"GROUP_FULL", "ALREADY_GROUP_MEMBER", "CANNOT_REMOVE_OWNER", "CANNOT_MUTE_OWNER",
+		"CANNOT_JOIN", "JOIN_REQUEST_PENDING", "GROUP_REQUEST_HANDLED",
+		"NOT_REQUEST_TARGET", "NO_ELIGIBLE_INVITEE", "NOT_MUTUAL_FOLLOW",
+		"INVITE_NOT_ACCEPTED", "STICKER_ALREADY_EXISTS", "INVALID_STICKER_URL",
+		"INVALID_SCHEDULE_PAYLOAD", "SCHEDULE_COLOR_DUPLICATED":
+		return http.StatusBadRequest
+	case "VERIFICATION_CODE_TOO_FREQUENT":
+		return http.StatusTooManyRequests
+	case "EMAIL_SERVICE_UNAVAILABLE", "VERIFICATION_CODE_UNAVAILABLE", "INTERNAL_ERROR":
+		return http.StatusInternalServerError
 	default:
 		return http.StatusBadRequest
 	}
 }
+
+// ErrorWithStringCode 带字符串错误码的错误响应
+func ErrorWithStringCode(c *gin.Context, statusCode int, code string, message string) {
+	c.JSON(statusCode, ResponseSnakeCase{
+		Code:    0, // 为了兼容，这里设为0，实际错误码在message中体现
+		Message: message,
+		Data:    code,
+	})
+}