refactor: standardize config structure and consolidate modules

- Standardized apps/ directory by renaming all entry points (e.g., home.nix) to default.nix and updating imports to use directory paths.
- Consolidated system/ logic into modules/system/, eliminating the top-level system/ directory and redundant wrappers.
- Merged subsidiary utility scripts (e.g., hakase-popup.nix, switch-wallpaper.nix) into their parent default.nix files for better cohesion.
- Cleaned up unused files and updated all module references to reflect the new structure.

modules/system/gaming.nix

@@ -1,5 +1,21 @@
-{
-  imports = [
-    ../../system/steam.nix
-  ];
-}
+{pkgs, ...}: {
+  hardware.graphics = {
+    enable = true;
+    enable32Bit = true; # For 32-bit games
+  };
+
+  programs.steam = {
+    enable = true;
+    remotePlay.openFirewall = true;
+    localNetworkGameTransfers.openFirewall = true;
+    extest.enable = true;
+    gamescopeSession.enable = true;
+    extraCompatPackages = with pkgs; [
+      proton-ge-bin
+    ];
+  };
+
+  programs.gamemode.enable = true;
+  # Fix slow Steam Download speeds
+  services.resolved.enable = true;
+}