Refactor: Simplify module structure and reorganize services

- Removed system/ directory, merged applications into users/geir.nix
- Simplified fonts.nix to bare minimum (users can add more)
- Moved transmission.nix to sleeper-service/services/ (machine-specific)
- Organized grey-area services into services/ directory
- Updated import paths and tested all configurations
- Added research documentation for deploy-rs and GNU Stow

machines/grey-area/services/jellyfin.nix

@@ -0,0 +1,9 @@
+{ config, pkgs, ... }:
+{
+  services.jellyfin = { 
+  	enable = true;
+	  group = "users";
+	};	
+  networking.firewall.allowedTCPPorts = [ 8096 8920 ];
+  networking.firewall.allowedUDPPorts = [ 1900 7359 ];
+}