Notification microservice — Messenger + RabbitMQ

Asynchronous notification microservice: email, SMS, Telegram, Slack. Notifications are stored in PostgreSQL, sent to RabbitMQ via Symfony Messenger. A separate worker processes the queue, routing through channels via match. Email through Symfony Mailer. API key authentication. Retry mechanism on errors. All code in PHP 8.4 attributes — readonly classes, #[Route], #[AsMessageHandler], #[MapRequestPayload]. Zero annotations.