Add Django site, Docker packaging, and beta/prod Gitea deploys.

Unignore site/ (was blocked by mkdocs /site rule), add compose/Docker/uv tooling, and split deploys so push to main goes to beta while prod stays manual.

site/core/views.py

@@ -0,0 +1,6 @@
+from django.http import JsonResponse
+
+
+def healthz(_request):
+    """Liveness probe for deploy / NPM health checks."""
+    return JsonResponse({"status": "ok"})