Add SEO, sitemap, robots, search, Meilisearch and security files

- JSON-LD: Organization, WebSite with SearchAction, BreadcrumbList
- SitemapController: sitemapindex with main + paginated events (images/videos)
- RobotsController: dynamic robots.txt with sitemap URL
- SearchController: /search with Meilisearch (TODO)
- Meilisearch added to dev and prod docker-compose
- Breadcrumbs added to all controllers
- .well-known: security.txt, humans.txt, dnt-policy.txt
- PGP public key in public/key.asc
- SecurityController: /mot-de-passe + .well-known/change-password route

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

templates/search/index.html.twig

@@ -0,0 +1,7 @@
+{% extends 'base.html.twig' %}
+
+{% block title %}Recherche - E-Ticket{% endblock %}
+
+{% block body %}
+
+{% endblock %}