[bojemoi] uzi: shell→meterpreter upgrade + fix Telegram chat_id

Commit `0cd3d6c`

Add upgrade_to_meterpreter(): injects msfvenom ELF stager via base64 into shell sessions, connects bind_tcp handler — no LHOST/reverse routing needed
Add handle_new_sessions(): auto-upgrades new shell sessions, deduplicates via upgraded_sessions set, then sends Telegram alert
Fix port conflict: kill stale stager on bind_port before injection (fuser -k)
Fix read_secret(): env var now takes priority over Docker secret file, allowing TELEGRAM_ALERT_CHAT_ID override without recreating shared secrets
Stack: add BIND_PORT=5556, PYTHONUNBUFFERED=1, TELEGRAM_ALERT_CHAT_ID=-5087117106

Co-Authored-By: Claude Sonnet 4.6 noreply@anthropic.com