gaming: declarative Flatpak via nix-flatpak (Bolt, Sober), Heroic + Proton-GE

Add nix-flatpak flake input and modules/gaming.nix managing Flatpak
remotes/packages declaratively: Bolt (Jagex launcher for RS3/OSRS) and
Sober (Roblox). Add Heroic and hyperplay-ext, plus Proton-GE for Steam.
Drops the old imperative runescape-launcher.

modules/gaming.nix

@@ -0,0 +1,26 @@
+# Gaming-related configuration
+# Flatpak is managed declaratively via nix-flatpak (see flake.nix input).
+{ config, pkgs, lib, ... }:
+
+{
+  # Proton-GE for Steam (better Jagex Launcher compatibility than stock Proton).
+  # Steam itself is enabled in modules/programs.nix.
+  programs.steam.extraCompatPackages = [ pkgs.proton-ge-bin ];
+
+  services.flatpak = {
+    enable = true;
+    remotes = [
+      { name = "flathub"; location = "https://dl.flathub.org/repo/flathub.flatpakrepo"; }
+    ];
+    packages = [
+      # Bolt: Jagex-account launcher for RuneScape 3 (NXT) and OSRS / RuneLite.
+      { appId = "com.adamcake.Bolt"; origin = "flathub"; }
+      # Sober: Roblox Player runtime (Android build via Flatpak) — no native Linux client.
+      { appId = "org.vinegarhq.Sober"; origin = "flathub"; }
+    ];
+    update.auto = {
+      enable = true;
+      onCalendar = "weekly";
+    };
+  };
+}

modules/packages.nix

@@ -14,6 +14,7 @@
     "terraform"
     "packer"
     "obsidian"
+    "hyperplay-ext"
   ];
 
   # List packages installed in system profile.
@@ -66,6 +67,9 @@
     obs-studio
     inputs.anotherim.packages.${pkgs.system}.default
 
+    # Gaming
+    heroic
+
     # Development
     nodejs_20
     gnupg