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

Makefile

@@ -0,0 +1,12 @@
+BINARY  := proxmox-backup-watch
+VERSION := $(shell cat VERSION)
+COMMIT  := $(shell git rev-parse --short HEAD 2>/dev/null || echo none)
+DATE    := $(shell date -u +%Y-%m-%dT%H:%M:%SZ)
+LDFLAGS := -s -w -X main.version=$(VERSION) -X main.commit=$(COMMIT) -X main.date=$(DATE)
+
+.PHONY: build clean
+build:
+	GOOS=linux GOARCH=amd64 CGO_ENABLED=0 go build -ldflags "$(LDFLAGS)" -o $(BINARY) .
+
+clean:
+	rm -f $(BINARY)