webserver: Use SIGKILL instead of SIGTERM

configuration/services/webserver.nix

@@ -34,6 +34,10 @@
 
     ports = [ "3002:3002" ];
     volumes = [ "tlaternet-mail:/srv/mail" ];
-    extraOptions = [ "--hostname=tlater.net" ];
+    extraOptions = [
+      "--hostname=tlater.net"
+      # Rocket 0.4 doesn't support SIGTERM anyway, so SIGKILL is the cleanest exit possible.
+      "--stop-signal=SIGKILL"
+    ];
   };
 }