gaming: install Minecraft Bedrock via nix-flatpak

Add the nix-flatpak flake input and wire its NixOS module into the gaming
module to declaratively install io.mrarm.mcpelauncher from Flathub. The
Flatpak build tracks the newer, pairip-protected Bedrock releases ahead of
the nixpkgs mcpelauncher package.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

modules/gaming.nix

@@ -1,6 +1,8 @@
-{ pkgs, ... }:
+{ inputs, pkgs, ... }:
 
 {
+  imports = [ inputs.nix-flatpak.nixosModules.nix-flatpak ];
+
   programs.steam = {
     enable = true;
     remotePlay.openFirewall = true;
@@ -17,4 +19,14 @@
     prismlauncher
     protonup-qt
   ];
+
+  # Minecraft Bedrock via mcpelauncher (unofficial; runs the Android ARM build
+  # through a libc shim — you must own Bedrock on Google Play). Installed as a
+  # Flatpak (io.mrarm.mcpelauncher) rather than the nixpkgs package, whose
+  # launcher lagged the newer, pairip-protected Bedrock releases. nix-flatpak
+  # adds the Flathub remote (its default) and installs the app on activation.
+  services.flatpak = {
+    enable = true;
+    packages = [ "io.mrarm.mcpelauncher" ];
+  };
 }