deploy: exclude worker heartbeat from host backup tar

The worker rewrites ./worker-heartbeat.json every poll interval
(10s); the host backup tar reads the same directory, so it
could hit 'file changed as we read it', exit 1, and abort the
deploy under set -e (this killed the PR #22 deploy). The
heartbeat file is regenerable runtime state, not code, so
excluding it from the backup is correct, not a workaround.

deploy/deploy.sh

@@ -125,7 +125,7 @@ wait_health() {
 }
 
 # 1. 备份当前代码（排除 work/，只留最近 3 份）
-tar --exclude='./work' -czf "$BACKUP_FILE" -C /opt codex-app-server
+tar --exclude='./work' --exclude='./worker-heartbeat.json' -czf "$BACKUP_FILE" -C /opt codex-app-server
 echo "已备份当前代码到：$BACKUP_FILE"
 ls -t "$BACKUP_DIR"/codex-app-server-*.tar.gz 2>/dev/null \
   | tail -n +4 | xargs -r rm -f