Add RAM sentinel daemon for OOM prevention

[idelcano]

📌 References
Issue: https://app.clickup.com/t/4528615/869e36g3p

📝 Implementation
Adds ram_sentinel.py, a daemon that monitors available RAM and stops
Monit-managed services when memory drops critically low, then restores
them once RAM recovers. Configured per-environment via systemd ExecStart
flags — no code changes needed between servers.

Key design decisions:

• Two stop strategies: kill (SIGKILL via Monit PID, for Java/Tomcat)
  and stop (clean monit stop, for Docker/Postgres)
• Services stopped in tier order, restored in reverse
• State persisted to /run/stopram/state.json so an interrupted recovery
  is resumed on daemon restart
• --dry-run mode reads RAM and PIDs for real but skips all destructive
  commands

How to install

1. Copy ram_sentinel.py to /usr/local/bin/ram_sentinel.py
2. Run a dry-run with the trigger set above current available RAM to
   force an emergency cycle and verify tier names and PID resolution:
   python3 /usr/local/bin/ram_sentinel.py
   --emergency-trigger <above_current_available_MB to test>
   --safe-recovery <target_MB>
   --tier kill:<monit_name>
   --dry-run
3. Confirm output shows correct PID found and [DRY-RUN] would... for
   each action
4. Create the appropriate .service file for the server to
   /etc/systemd/system/ram-sentinel.service
5. Enable and start the service:
   systemctl daemon-reload && systemctl enable --now ram-sentinel
   journalctl -u ram-sentinel -f