Fix SSH agent and systemd service race conditions

- bw-ssh-keys.service: use ssh-agent.service, add SSH_AUTH_SOCK env
- Stage 08: enable ssh-agent.socket, mask gcr-ssh-agent before services
- Stage 11: remove SSH agent section (moved to stage 08 for ordering)
- Stage 09: remove stale bw-load-ssh autostart config
- .zshrc: export SSH_AUTH_SOCK to match OpenSSH agent socket
- Remove config/autostart/ (no longer needed)
- porridge daemon: no longer exits on missing API key;
  add SIGHUP handler for live config reload

stages/11-tweaks.sh

@@ -41,5 +41,4 @@ EOF
   fi
   $SERVICE_ENABLE powertop 2>/dev/null && ok "PowerTOP auto-tune enabled." || true
 fi
-
 ok "Stage 11 complete: system tweaks applied."