Drop qt_users dependency for configs and track app version

internal/models/configuration.go

@@ -42,8 +42,9 @@ func (c ConfigItems) Total() float64 {
 type Configuration struct {
 	ID             uint        `gorm:"primaryKey;autoIncrement" json:"id"`
 	UUID           string      `gorm:"size:36;uniqueIndex;not null" json:"uuid"`
-	UserID         uint        `gorm:"not null" json:"user_id"` // Legacy owner field (kept for backward compatibility)
+	UserID         *uint       `json:"user_id,omitempty"` // Legacy field, no longer required for ownership
 	OwnerUsername  string      `gorm:"size:100;not null;default:'';index" json:"owner_username"`
+	AppVersion     string      `gorm:"size:64" json:"app_version,omitempty"`
 	Name           string      `gorm:"size:200;not null" json:"name"`
 	Items          ConfigItems `gorm:"type:json;not null" json:"items"`
 	TotalPrice     *float64    `gorm:"type:decimal(12,2)" json:"total_price"`