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/hyprland.nix

@@ -1,5 +1,29 @@
 {
-  imports = [
-    ../../apps/hyprland/default.nix
+  myConfig,
+  inputs,
+  pkgs,
+  ...
+}: {
+  programs.hyprland = {
+    enable = true;
+    package = inputs.hyprland.packages.${pkgs.stdenv.hostPlatform.system}.hyprland;
+    portalPackage = inputs.hyprland.packages.${pkgs.stdenv.hostPlatform.system}.xdg-desktop-portal-hyprland;
+    withUWSM = true;
+  };
+
+  environment.systemPackages = [
+    pkgs.hyprpicker
+    pkgs.hyprlock
+    pkgs.hypridle
+    pkgs.hyprpaper
+    pkgs.hyprsunset
+    pkgs.hyprpolkitagent
   ];
-}
+
+  xdg.terminal-exec = {
+    enable = true;
+    settings = {
+      default = ["${myConfig.terminal.default}"];
+    };
+  };
+}