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>

composer.json

@@ -107,6 +107,8 @@
         }
     },
     "require-dev": {
+        "friendsofphp/php-cs-fixer": "^3.94",
+        "phpstan/phpstan": "^2.1",
         "phpunit/phpunit": "^13.0",
         "symfony/browser-kit": "8.0.*",
         "symfony/css-selector": "8.0.*",