Concurrent webhook failures can send duplicate "webhook paused" alerts at the retry threshold

### 👟 Reproduction steps The webhooks worker's failure branch is not concurrency-safe around the retry-threshold transition. When two failing deliveries for the same webhook are processed concurrently (two subscribed events dispatched close together), both handlers can independently cross the threshold and each enqueue a "paused" notification. 1. Configure a webhook whose target returns an error (e.g. a non-existent URL or a 5xx endpoint) and subscribe it to a frequently-emitted event. 2. Set `_APP_WEBHOOK_MAX_FAILED_ATTEMPTS` to `10` (default) and drive `attempts` to `9`. 3. Emit two subscribed events in quick succession so two `v1-webhooks` worker handlers run concurrently for the same webhook. 4. Observe the notification recipient's inbox / notification queue. ### 👍 Expected behavior Crossing the failure threshold is a single logical event, so exactly one "webhook paused" alert should be sent per pause cycle. ### 👎 Actual Behavior Both concurrent handlers can send a "paused" alert, producing duplicate notifications for one threshold transition. Root cause (`src/Appwrite/Platform/Workers/Webhooks.php`, lines 164–192 — permalink below): ```php $dbForPlatform->increaseDocumentAttribute('webhooks', $webhook->getId(), 'attempts', 1); // L165 atomic $webhook = $dbForPlatform->getDocument('webhooks', $webhook->getId()); // L166 reload $attempts = $webhook->getAttribute('attempts'); // L167 // ... if ($attempts >= \intval(System::getEnv('_APP_WEBHOOK_MAX_FAILED_ATTEMPTS', '10'))) { // L185 $webhook->setAttribute('enabled', false); $updatePayload['enabled'] = false; $this->sendAlert(...); // L188 alert BEFORE persist } $dbForPlatform->updateDocument('webhooks', $webhook->getId(), new Document($updatePayload)); // L191 persist enabled=false ``` Although the increment at L165 is atomic, the threshold check (L185) and `sendAlert` …