feat: Robotex landing on robotex.sokolab.xyz and announcement post

- projects section: standalone landing template and styles, served on a
  subdomain by the ingress Caddy (project) snippet
- Robotex landing in RU/EN, links to Redmine forum/issues
- blog post: Robotex is now a free service

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

content/projects/_index.md

@@ -0,0 +1,6 @@
+---
+title: "Проекты"
+build:
+  render: never
+  list: never
+---