Extract searchEvents() to EventIndexService, reduce duplication across controllers

- Add searchEvents() method: Meilisearch search with DB fallback
- Use in HomeController, AdminController, AccountController (removes ~45 duplicated lines)
- Add assets/vendor/ to ESLint ignores
- Update EventIndexServiceTest for new constructor

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

eslint.config.js

@@ -27,6 +27,6 @@ export default [
         },
     },
     {
-        ignores: ["node_modules/", "public/build/", "vendor/", "public/sw.js", "public/workbox/", "public/idb/"],
+        ignores: ["node_modules/", "public/build/", "vendor/", "public/sw.js", "public/workbox/", "public/idb/", "assets/vendor/"],
     },
 ];