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>

.stylelintrc.json

@@ -0,0 +1,10 @@
+{
+    "extends": "stylelint-config-standard-scss",
+    "rules": {
+        "at-rule-no-unknown": null,
+        "scss/at-rule-no-unknown": [true, {
+            "ignoreAtRules": ["use", "tailwind", "apply", "variants", "responsive", "screen", "layer"]
+        }],
+        "no-descending-specificity": null
+    }
+}