feat(nfs): centralize nixdesk jellyfin nfs client module

Move the nixdesk jellyfin NFS client configuration from individual
host services to a centralized NixOS module in `modules/system/nfs/`.

This change:
- Creates `modules/system/nfs/default.nix` containing the `nixdeskJellyfin`
  flake module.
- Removes redundant NFS client definitions from `modules/hosts/nix-server/`
  and `modules/hosts/r5500/`.
- Updates `modules/hosts/r5500/configuration.nix` to use the new
  centralized module.
- Cleans up unused local disk configuration in `modules/hosts/14900k/`.

modules/hosts/14900k/_private/media-disk.nix

@@ -1,9 +1,5 @@
 # Extra local disks. Declared here, not in hardware.nix (hardware.nix is generated).
 { config, lib, ... }:
-let
-  # Stable UID so NTFS `uid=` matches `users.users.olivier` (override if your account is not 1000).
-  olivierUid = config.users.users.olivier.uid or 1000;
-in
 {
   users.users.olivier.uid = lib.mkDefault 1000;
   # LABEL="MediaLibrary" (btrfs on sda1 by UUID). No subvol=@ — this disk has no @ subvolume.
@@ -33,15 +29,4 @@ in
   # LABEL="Deep Storage Unit". Owner olivier, group nfsmedia (990) so:
   # - local logins write as user 1000 (owner rwx);
   # - NFS (all_squash → uid/gid 990) matches group 990 → rwx (see jellyfin-nfs-export).
-  #fileSystems."/mnt/test" = {
-  #  device = "/dev/disk/by-uuid/BC12E55E12E51DE0";
-  #  fsType = "ntfs-3g";
-  #  options = [
-  #    "rw"
-  #    "force"
-  #    "uid=${toString olivierUid}"
-  #    "gid=990"
-  #    "umask=0002"
-  #  ];
-  #};
 }

modules/hosts/nix-server/_services/nixdesk-nfs-client.nix

@@ -1,35 +0,0 @@
-# NFS mounts of nixdesk (14900k) bulk storage for nix-server. Exports live in
-#   modules/hosts/14900k/_private/jellyfin-nfs-export.nix
-#
-# Jellyfin library paths (see also services/jellyfin.nix):
-#   Movies → /mnt/nixdesk-jellyfin/movies
-#   Shows  → /mnt/nixdesk-jellyfin/tv
-#
-# If you see "Stale file handle" under /mnt after changing exports or fsid on nixdesk, drop the
-# old client mount and let automount reattach, e.g.:
-#   sudo umount -l /mnt/nixdesk-jellyfin
-#   ls /mnt/nixdesk-jellyfin
-# (or reboot nix-server.)
-{ ... }:
-let
-  nfsExportHost = "192.168.2.25";
-  # nfsvers+tcp: predictable Linux↔Linux; lookupcache=none: fewer stale dentries after export changes.
-  nfsClientOpts = [
-    "rw"
-    "noatime"
-    "nofail"
-    "_netdev"
-    "nfsvers=3"
-    "tcp"
-    "lookupcache=none"
-    "x-systemd.automount"
-    "x-systemd.idle-timeout=3600"
-  ];
-in
-{
-  fileSystems."/mnt/nixdesk-jellyfin" = {
-    device = "${nfsExportHost}:/mnt/deep/jellyfin";
-    fsType = "nfs";
-    options = nfsClientOpts;
-  };
-}

modules/hosts/r5500/_services/nixdesk-nfs-client.nix

@@ -1,28 +0,0 @@
-# NFS mounts of nixdesk (14900k) bulk storage for r5500. Exports live in
-#   modules/hosts/14900k/_private/jellyfin-nfs-export.nix
-#
-# Jellyfin library paths:
-#   Movies → /mnt/nixdesk-jellyfin/movies
-#   Shows  → /mnt/nixdesk-jellyfin/tv
-{ ... }:
-let
-  nfsExportHost = "192.168.2.25";
-  nfsClientOpts = [
-    "rw"
-    "noatime"
-    "nofail"
-    "_netdev"
-    "nfsvers=3"
-    "tcp"
-    "lookupcache=none"
-    "x-systemd.automount"
-    "x-systemd.idle-timeout=3600"
-  ];
-in
-{
-  fileSystems."/mnt/nixdesk-jellyfin" = {
-    device = "${nfsExportHost}:/mnt/deep/jellyfin";
-    fsType = "nfs";
-    options = nfsClientOpts;
-  };
-}

modules/hosts/r5500/configuration.nix

@@ -17,7 +17,7 @@
         ./_private/media-disk.nix
         ./_private/media-paths.nix
         ./_services/docker-media.nix
-        ./_services/nixdesk-nfs-client.nix
+        self.nixosModules.nixdeskJellyfin
         ./_services/jellyfin.nix
         ./_services/sonarr.nix
         ./_services/radarr.nix