Configure for atlas/pinj and add Wayland session variables

- Rename hosts/hostname/ to hosts/atlas/
- Replace all <hostname> placeholders with 'atlas'
- Replace all <username> placeholders with 'pinj'
- Set timezone to Europe/Rome (with TODO note to change if needed)
- Set locale to en_US.UTF-8
- Add Wayland session variables (QT_QPA_PLATFORM, MOZ_ENABLE_WAYLAND,
  NIXOS_OZONE_WL) for proper app integration
- Remove placeholder comments that are no longer needed

https://claude.ai/code/session_01UAdmEkSeh9NGPfjRfViLWY

modules/gaming.nix

@@ -53,14 +53,12 @@
   # programs to function correctly. These groups are only added when using
   # the gaming profile. If you need consistent group membership across
   # both profiles, add these groups to common.nix instead.
-  # IMPORTANT: Replace <username> with actual username
-  users.users.<username>.extraGroups = [ "corectrl" "gamemode" ];
+  users.users.pinj.extraGroups = [ "corectrl" "gamemode" ];
 
   # --------------------------------------------------------------------------
   # GAMING PACKAGES
   # --------------------------------------------------------------------------
-  # IMPORTANT: Replace <username> with actual username
-  users.users.<username>.packages = with pkgs; [
+  users.users.pinj.packages = with pkgs; [
     # -- Performance Overlays --
     mangohud        # FPS counter, GPU stats
     goverlay        # MangoHud GUI config