docs(services): note the restic-nomarchy list/restore wrapper

VM-verified the full batch of opt-in service toggles (libvirt, docker, obs
+ v4l2loopback, ollama, printing, openrgb, wireshark, adb, gamemode,
kdeconnect, restic) in a headless nixosTest — all green, no module bugs.

The one thing worth surfacing: services.restic ships a pre-configured
`restic-nomarchy` wrapper (repository + passwordFile baked in) for listing
and restoring snapshots. Mention it in the option description and README so
the restore path is discoverable — a backup you can't restore is half a
feature.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

modules/nixos/services.nix

@@ -86,7 +86,9 @@ in
       enable = lib.mkEnableOption ''
         a scheduled (daily) restic backup — headless, complementing the Pika
         GUI. Backs up `paths` with sane retention (7 daily / 4 weekly /
-        6 monthly); needs a `repository` and a `passwordFile` (below)'';
+        6 monthly); needs a `repository` and a `passwordFile` (below). List
+        and restore with the generated `restic-nomarchy` wrapper (repo +
+        password baked in), e.g. `restic-nomarchy snapshots`'';
 
       repository = lib.mkOption {
         type = lib.types.str;