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>

eslint.config.js

@@ -0,0 +1,16 @@
+export default [
+    {
+        files: ["assets/**/*.js"],
+        rules: {
+            "no-unused-vars": "warn",
+            "no-undef": "error",
+            "no-console": "warn",
+            "eqeqeq": "error",
+            "no-var": "error",
+            "prefer-const": "warn",
+        },
+    },
+    {
+        ignores: ["node_modules/", "public/build/", "vendor/"],
+    },
+];