jellyfin: patch port 8096 being open

All jellyfin traffic should actually go through caddy.
This port being open caused a lot of confusion for me.
As I was getting traffic from typo'd domain names,
such as `jellfin.gardling.com`, which made NO SENSE!
But since it was going directly via port 8096, it
skipped caddy entirely so the traffic went through.

tests/fail2ban-jellyfin.nix

@@ -55,6 +55,9 @@ pkgs.testers.runNixOSTest {
           jellyfinModule
         ];
 
+        # needed for testing
+        services.jellyfin.openFirewall = true;
+
         # Create the media group
         users.groups.media = { };