Implement r5500 media stack configuration with NFS and Docker services

- Added configuration for media stack on r5500, including paths for Jellyfin, Sonarr, Radarr, and other media services.
- Integrated NFS client for accessing Jellyfin libraries from nixdesk.
- Established Docker services for Dispatcharr and Organizr, including necessary user and group setups.
- Created systemd services for managing media directories and ensuring proper permissions.

modules/hosts/r5500/_private/media-stack-paths.nix

@@ -0,0 +1,16 @@
+# Path constants for the r5500 media stack (imported by _services/* and media-paths.nix).
+{
+  mediaRoot = "/mnt/media-stack";
+  downloadsDir = "/mnt/media-stack/downloads";
+  downloadsIncompleteDir = "/mnt/media-stack/downloads/incomplete";
+  sonarrDataDir = "/mnt/media-stack/sonarr";
+  radarrDataDir = "/mnt/media-stack/radarr";
+  prowlarrDataDir = "/mnt/media-stack/prowlarr";
+  qbittorrentDataDir = "/mnt/media-stack/qbittorrent";
+  seerrConfigDir = "/mnt/media-stack/seerr";
+  dispatcharrDataDir = "/mnt/media-stack/dispatcharr";
+  organizrDataDir = "/mnt/media-stack/organizr";
+  jellyfinConfigDir = "/mnt/media-stack/jellyfin/config";
+  jellyfinMoviesDir = "/mnt/media-stack/jellyfin/movies";
+  jellyfinTvDir = "/mnt/media-stack/jellyfin/tv";
+}