Add pve-backup-watch 0.0.1

A Go CLI that waits for a Proxmox VE vzdump backup to finish and
then restarts the guest.

- Take one or more VMIDs and poll the node's vzdump tasks via pvesh
- Handle QEMU VMs (qm) and LXC containers (pct): unlock, graceful
  shutdown with forced stop after 120s, then start
- Restart after any result by default; -only-failed restarts only when
  the backup did not finish OK, and -warn-ok treats warnings as success
- Ignore backups that finished before the tool started
- Add -dry-run, -timeout, -interval and -node options
- Exit with 0, 1 (failure or timeout) or 2 (usage error)
- Embed version, commit and build date via ldflags (VERSION file, Makefile)
- Add README and CHANGELOG

go.mod

@@ -0,0 +1,3 @@
+module proxmox-backup-watch
+
+go 1.21