[nix-deck] Use NixOS unstable for better Jovian compatibility

- Switch nix-deck to use nixpkgs-unstable and unstable home-manager/plasma-manager
- Remove jovian-compat.nix shim (not needed on unstable)
- Add bitwarden-desktop compatibility overlay for stable/unstable coexistence
- Update hardware-configuration.nix with actual Steam Deck hardware detection
- Add 8GB swap file configuration
- Configure AMD CPU microcode updates

This allows nix-deck to work with the latest Jovian-NixOS while keeping other
machines on stable 25.05.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

home/roles/desktop/default.nix

@@ -13,7 +13,7 @@ in
   config = mkIf cfg.enable {
     home.packages = with pkgs; [
       # Desktop applications
-      bitwarden
+      bitwarden-desktop
       dunst
       keepassxc
       unstable.ghostty