feat(pbs): post-install menu for Proxmox Backup Server

- Open the post-install menu from the PBS menu
- List only the customizable options that apply to PBS
- Offer the PBS no-subscription repository through the native repository API
- Upgrade PBS with the package list shown before applying it
- Remove and restore the subscription notice on the PBS web interface
- Install Figurine on PBS without the Proxmox VE aliases
- Offer the Helper-Scripts PBS post-install and microcode scripts
- Tune firewall bridges after the systemd udev rules in the automated post-install
- Add PBS repository policy tests and syntax checks
- Document the PBS differences on the post-install page
- Use backups in the Spanish PBS update message

AppImage/lib/use-platform.ts

@@ -0,0 +1,8 @@
+import useSWR from "swr"
+import { fetchApi } from "./api-config"
+
+// Shares the dashboard's /api/platform request through the SWR cache.
+export function useIsPbs(): boolean {
+  const { data } = useSWR<{ product: string }>("/api/platform", (url: string) => fetchApi<{ product: string }>(url), { revalidateOnFocus: false })
+  return data?.product === "pbs"
+}