feat(yggdrasil): implement standard error responses and UUID format improvements

- Add YggdrasilErrorResponse struct and standard error codes for protocol compliance
- Change UUID storage from varchar(36) to varchar(32) for unsigned format
- Add utility functions: GenerateUUID, FormatUUIDToNoDash, RandomHex
- Support unsigned query parameter in GetProfileByUUID endpoint
- Improve refresh token response with available profiles list
- Fix key pair retrieval to use correct database column (rsa_private_key)
- Update UUID validator to accept both 32-char and 36-char formats
- Add SignStringWithProfileRSA method for profile-specific signing
- Fix profile assignment validation in refresh token flow

internal/service/yggdrasil_service_composite.go

@@ -85,8 +85,8 @@ func (s *yggdrasilServiceComposite) JoinServer(ctx context.Context, serverID, ac
 		return fmt.Errorf("验证Token失败: %w", err)
 	}
 
-	// 格式化UUID并验证与Token关联的配置文件
-	formattedProfile := utils.FormatUUID(selectedProfile)
+	// 确保UUID是32位无符号格式（用于向后兼容）
+	formattedProfile := utils.FormatUUIDToNoDash(selectedProfile)
 	if uuid != formattedProfile {
 		return errors.New("selectedProfile与Token不匹配")
 	}
@@ -115,6 +115,11 @@ func (s *yggdrasilServiceComposite) SerializeProfile(ctx context.Context, profil
 	return s.serializationService.SerializeProfile(ctx, profile)
 }
 
+// SerializeProfileWithUnsigned 序列化档案（支持unsigned参数）
+func (s *yggdrasilServiceComposite) SerializeProfileWithUnsigned(ctx context.Context, profile model.Profile, unsigned bool) map[string]interface{} {
+	return s.serializationService.SerializeProfileWithUnsigned(ctx, profile, unsigned)
+}
+
 // SerializeUser 序列化用户
 func (s *yggdrasilServiceComposite) SerializeUser(ctx context.Context, user *model.User, uuid string) map[string]interface{} {
 	return s.serializationService.SerializeUser(ctx, user, uuid)