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/tte/default.nix

@@ -0,0 +1,14 @@
+{pkgs, ...}: let
+  hakase-screensaver-launch = pkgs.writeShellScriptBin "hakase-cmd-screensaver" ''
+    # Placeholder for actual screensaver logic if needed
+    echo "Screensaver placeholder"
+  '';
+in {
+  home.packages = with pkgs; [
+    terminaltexteffects
+    hakase-screensaver-launch
+  ];
+  home.file.".config/hakase/branding/screensaver.txt" = {
+    source = ../../assets/branding.txt;
+  };
+}

apps/tte/hakase-screensaver.nix

@@ -1,14 +0,0 @@
-{
-  pkgs,
-  lib,
-  ...
-}: let
-  #
-  hakase-screensaver-launch = pkgs.writeShellScriptBin "hakase-cmd-screensaver" ''
-
-  '';
-in {
-  home.packages = with pkgs; [
-    hakase-screensaver-launch
-  ];
-}

apps/tte/home.nix

@@ -1,8 +0,0 @@
-{pkgs, ...}: {
-  home.packages = with pkgs; [
-    terminaltexteffects
-  ];
-  home.file.".config/hakase/branding/screensaver.txt" = {
-    source = ../../assets/branding.txt;
-  };
-}