fix: address audit findings for notify, websearch and security

- Fix GetByKeyForAuth missing user.FieldEmail and user.FieldUsername (notifications sent to empty address)
- Guard against empty email in collectBalanceNotifyRecipients
- Remove non-atomic TotalRecharged read-modify-write in admin balance adjustment
- HTML-escape userName/siteName/accountName in notification email templates
- Fix timer leak in ProfileBalanceNotifyCard (add onUnmounted cleanup)
- Add warning log on websearch proxy URL resolution failure

backend/internal/repository/api_key_repo.go

@@ -139,6 +139,8 @@ func (r *apiKeyRepository) GetByKeyForAuth(ctx context.Context, key string) (*se
 		WithUser(func(q *dbent.UserQuery) {
 			q.Select(
 				user.FieldID,
+				user.FieldEmail,
+				user.FieldUsername,
 				user.FieldStatus,
 				user.FieldRole,
 				user.FieldBalance,