Add CI pipeline, Meilisearch service, CacheService and code quality tools

- CI: lint, PHPStan, PHP CS Fixer, ESLint, Stylelint, security audit, build
- MeilisearchService: async via Messenger, sync search
- MeilisearchMessage + handler for async operations
- CacheService with CacheKey enum (TTL per key, remember pattern)
- Meilisearch env vars in .env.local, vault and env.local.j2
- Messenger routing for MeilisearchMessage
- PHPStan level 6, ESLint, Stylelint configs

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/Message/MeilisearchMessage.php

@@ -0,0 +1,12 @@
+<?php
+
+namespace App\Message;
+
+class MeilisearchMessage
+{
+    public function __construct(
+        public readonly string $action,
+        public readonly string $index,
+        public readonly array $payload = [],
+    ) {}
+}