fix: address audit findings for websearch and balance notification

- Fix GetByKeyForAuth not selecting balance notify fields (notifications
  never triggered in gateway path)
- Fix provider-level ProxyURL never resolved: inject ProxyRepository into
  SettingService, resolve proxy URLs when building Manager
- Fix admin manual balance adjustment not updating total_recharged
- Add threshold_type input validation (reject invalid values)
- Fix user threshold_type inheritance: custom threshold defaults to "fixed"
  instead of inheriting global type (prevents $5 being treated as 5%)
- Add try-catch for clipboard.writeText (fails on non-HTTPS)
- Add SetTotalRecharged to user Update for admin balance operations

backend/internal/service/user_service.go

@@ -145,7 +145,9 @@ func (s *UserService) UpdateProfile(ctx context.Context, userID int64, req Updat
 		user.BalanceNotifyEnabled = *req.BalanceNotifyEnabled
 	}
 	if req.BalanceNotifyThresholdType != nil {
-		user.BalanceNotifyThresholdType = *req.BalanceNotifyThresholdType
+		if *req.BalanceNotifyThresholdType == ThresholdTypeFixed || *req.BalanceNotifyThresholdType == ThresholdTypePercentage {
+			user.BalanceNotifyThresholdType = *req.BalanceNotifyThresholdType
+		}
 	}
 	if req.BalanceNotifyThreshold != nil {
 		if *req.BalanceNotifyThreshold <= 0 {