Add V-Rising dedicated server via Docker on FredOS-Mediaserver

Uses NixOS virtualisation.oci-containers (Docker backend) with the
trueosiris/vrising image. Persists server files and save data under
/var/lib/v-rising/. Opens UDP 9876/9877 in the firewall.

https://claude.ai/code/session_01Ays1x4CUUJE1jPLkeNMojV

common.nix

@@ -32,6 +32,7 @@
     ./services/authelia.nix
     ./services/homepage.nix
     ./services/arr-interconnect.nix
+    ./services/v-rising.nix
   ];
 
   ### Make build time quicker