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.

apps/stylix/default.nix

@@ -0,0 +1,39 @@
+{
+  pkgs,
+  inputs,
+  myConfig,
+  lib,
+  ...
+}: {
+  imports = [
+    inputs.stylix.homeModules.stylix
+  ];
+  stylix = {
+    autoEnable = false;
+    targets = {
+      firefox = {
+        enable = false;
+        colorTheme.enable = true;
+        profileNames = [
+          "hakase"
+        ];
+      };
+      hyprpaper.enable = true;
+      hyprlock.enable = true;
+      gtk.enable = true;
+    };
+    enable = true;
+    # autoEnable = false;
+    image = ../../assets/Wallpapers/${myConfig.hyprland.wallpaper};
+    polarity = "dark";
+    # base16Scheme = lib.mkDefault {
+    #   generator = "vibrant";
+    # };
+    iconTheme = {
+      enable = true;
+      package = pkgs.papirus-icon-theme; # The package to install
+      dark = "Papirus-Dark"; # The theme name for dark mode
+      light = "Papirus-Light"; # The theme name for light mode
+    };
+  };
+}