feat: add AMD GPU tools, media packages, and productivity module

Task 3 - Gaming profile:
- Add gpu.nix with ROCm runtime/smi/info and vulkan-tools
- Import gpu.nix in gaming profile aggregator

Task 4 - Media profile:
- Add unimatrix to yt-dlp.nix packages
- (plexamp, webcord, mpv config were already present)

Task 5 - Desktop apps:
- Add productivity.nix with pomodoro-timer
- Import productivity.nix in desktop apps aggregator

home/profiles/media/yt-dlp.nix

@@ -13,6 +13,7 @@ in {
   config = mkIf cfg.enable {
     home.packages = with pkgs; [
       plexamp
+      unimatrix
       webcord
     ];