Applied Codex's security and reliability recommendations:
**SSH Key Safety:**
- Added "pulse-managed-key" comment marker to all SSH keys
- Removal now targets only marked keys (prevents deleting operator keys)
- Uses atomic file replacement via mktemp for authorized_keys edits
**Idempotency Improvements:**
- LXC config glob now uses nullglob to handle empty directories
- pveum token removal handles missing users gracefully (|| printf '')
- All systemctl operations wrapped with || true for non-systemd hosts
- sed operations in loops protected with || true
**Container Detection:**
- Validates container is running before IP check (pct status)
- Confirms container exists with pct config before proceeding
- Uses printf '' instead of || true for command substitution
- Handles IPv6 and multi-IP scenarios more reliably
**Network Operations:**
- curl now uses --fail --show-error --silent --location
- Error messages visible to users instead of silenced
- Better diagnostics when download fails
**Migration Safety:**
- Verifies pulse-sensor-proxy service is active before key removal
- Fallback check for binary existence if systemd unavailable
- Preserves legacy SSH keys if proxy not confirmed healthy
- Clear messaging about deferred cleanup
All cleanup operations are now fully idempotent and safe for
repeated execution, even on partially-configured hosts.
Addresses #123
096801e96a