Separate JSON API backend (vm_api.py) + React+TanStack frontend scaffold

- vm_api.py: pure FastAPI JSON API on :8098 with CORS
- vm-api.service: systemd unit for API (replaces inline HTML vm_web.py for frontend)
- vm_web.py: kept intact as fallback; Apache now proxies /api/ -> :8098
- frontend/: Vite + React + TanStack Query scaffold
- Apache vhost updated: DocumentRoot -> frontend/dist, /api/ proxy, SPA fallback
- All original HTML pages still functional via :8099 during transition

frontend/node_modules/postcss/lib/stringify.d.ts

@@ -0,0 +1,9 @@
+import { Stringifier } from './postcss.js'
+
+interface Stringify extends Stringifier {
+  default: Stringify
+}
+
+declare let stringify: Stringify
+
+export = stringify