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/admin_service.go

@@ -709,6 +709,12 @@ func (s *adminServiceImpl) UpdateUserBalance(ctx context.Context, userID int64,
 		return nil, fmt.Errorf("balance cannot be negative, current balance: %.2f, requested operation would result in: %.2f", oldBalance, user.Balance)
 	}
 
+	// Track cumulative recharge for percentage-based balance notifications
+	balanceDelta := user.Balance - oldBalance
+	if balanceDelta > 0 {
+		user.TotalRecharged += balanceDelta
+	}
+
 	if err := s.userRepo.Update(ctx, user); err != nil {
 		return nil, err
 	}