fix: deadlock on user deletion — webhook handler never checked intentional mark

mark_intentional_panel_deletion was called before api.delete_user,
but _is_intentional_panel_deletion_event was never called in the
webhook handler — it was dead code. The user.deleted webhook processed
unconditionally, causing a deadlock between delete_user_account (Tx1
holding subscription row locks) and the webhook handler (Tx2 trying
to lock the same rows via decrement_subscription_server_counts).

Fix: check _is_intentional_panel_deletion_event at the top of
_handle_user_deleted — if True, log and return immediately without
touching the DB.

app/services/remnawave_webhook_service.py

@@ -994,6 +994,16 @@ class RemnaWaveWebhookService:
     async def _handle_user_deleted(
         self, db: AsyncSession, user: User, subscription: Subscription | None, data: dict
     ) -> None:
+        # Suppress webhook if this deletion was initiated by delete_user_account —
+        # prevents deadlock between the ongoing deletion transaction and this handler
+        if self._is_intentional_panel_deletion_event(data):
+            logger.info(
+                'Webhook user.deleted suppressed — intentional panel deletion in progress',
+                user_id=user.id,
+                uuid=data.get('uuid'),
+            )
+            return
+
         user_id = user.id
         sub_id = subscription.id if subscription else None