[katbyte]

The scheduled sync has been running twice at once; this makes it run once.

Why: every sync slot did the same work as two concurrent processes: double the GitHub API calls, and two writers stamping the same project items at the same time.

The crontab was registered twice. entry.sh writes the crontab to /etc/cron.d/crontab and then installs it with crontab. Alpine's dcron also reads /etc/cron.d by itself, so it saw the job in both places. A once-a-minute job in a plain Alpine container with those exact lines fires twice in the same second:

job ran: 21:34:01
job ran: 21:34:01

The file now lives in /app, so only the copy crontab installs exists; the same test fires once a minute.

-echo "$SYNC_CRON /app/scripts/run.sh 2>&1 | tee -a /var/log/ghp-sync.log" > /etc/cron.d/crontab
-chmod 0644 /etc/cron.d/crontab
-crontab /etc/cron.d/crontab
+echo "$SYNC_CRON /app/scripts/run.sh 2>&1 | tee -a /var/log/ghp-sync.log" > /app/crontab
+crontab /app/crontab

Fine as it is: the rest of entry.sh (the env copy, the log tail) is unchanged; shellcheck passes.