fix bug constrain not found on postgres

Signed-off-by: freedisch <freeproduc@gmail.com>

Author: Freedisch

havril/pkg/models/users.go

@@ -17,7 +17,7 @@ type User struct {
 	TokenHash             string `gorm:"uniqueIndex"`
 	TokenPrefix           string
 	TokenExpiresAt        *time.Time
-	RefreshTokenHash      string
+	RefreshTokenHash      string  `gorm:"uniqueIndex"`
 	RefreshTokenPrefix    string
 	RefreshTokenExpiresAt *time.Time
 	McpTokenHash          string