chore: remove kit stack

Remove kit service and related configuration:
- Removed kit from compose includes
- Deleted kit/compose.yaml (landing, vert, pastel, stirling, units, draw, figlet)
- Removed KIT env vars from arty.yml

Kit services were stateless and don't require data migration.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

compose.yaml

@@ -9,7 +9,6 @@ include:
   - links/compose.yaml
   - vault/compose.yaml
   - joplin/compose.yaml
-  - kit/compose.yaml
   - drop/compose.yaml
   - ai/compose.yaml
   - asciinema/compose.yaml