Remove complex SIGHUP reload feature, use simple restart instead

- Remove tokio signal handling and mutex-based TLS acceptor reloading
- Simplify main loop back to basic connection acceptance
- Update systemd service to remove ExecReload
- Change certbot hook to use systemctl restart instead of reload
- Maintain <1s restart time for certificate updates
- Eliminate user confusion about partial config reloading

dist/pollux.service

@@ -6,7 +6,6 @@ Wants=network.target
 [Service]
 Type=simple
 ExecStart=/usr/local/bin/pollux
-ExecReload=/bin/kill -HUP $MAINPID
 Restart=on-failure
 RestartSec=5
 User=gemini