feat: add gaming/media packages and nvidia finegrained power management

- nvidia.nix: set powerManagement.finegrained = false explicitly
- packages.nix: add libva-utils, vdpauinfo, lazydocker, mangohud
- configuration.nix: enable programs.gamemode

https://claude.ai/code/session_01JwjdjwvgMGW4TcpYi4MZ6n

configuration.nix

@@ -91,6 +91,8 @@
     dedicatedServer.openFirewall = true;
   };
 
+  programs.gamemode.enable = true;
+
   services.tailscale.enable = true;
   virtualisation.docker.enable = true;
 

nvidia.nix

@@ -7,6 +7,7 @@
     nvidia = {
       modesetting.enable = true;
       powerManagement.enable = true;
+      powerManagement.finegrained = false;
       open = false;
       nvidiaSettings = true;
     };

packages.nix

@@ -23,5 +23,11 @@
     # dev
     vscode
     docker-compose
+
+    # gaming / media
+    libva-utils
+    vdpauinfo
+    lazydocker
+    mangohud
   ];
 }