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/profile_service.go

@@ -4,6 +4,7 @@ import (
 	"carrotskin/internal/model"
 	"carrotskin/internal/repository"
 	"carrotskin/pkg/database"
+	"carrotskin/pkg/utils"
 	"context"
 	"crypto/rand"
 	"crypto/rsa"
@@ -12,7 +13,6 @@ import (
 	"errors"
 	"fmt"
 
-	"github.com/google/uuid"
 	"go.uber.org/zap"
 	"gorm.io/gorm"
 )
@@ -64,7 +64,7 @@ func (s *profileService) Create(ctx context.Context, userID int64, name string)
 	}
 
 	// 生成UUID和RSA密钥
-	profileUUID := uuid.New().String()
+	profileUUID := utils.GenerateUUID()
 	privateKey, err := generateRSAPrivateKeyInternal()
 	if err != nil {
 		return nil, fmt.Errorf("生成RSA密钥失败: %w", err)