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/home/hyprland.nix

@@ -1,13 +1,11 @@
 {
   imports = [
-    ../../apps/tte/hakase-screensaver.nix
-    ../../apps/hyprland/home.nix
-    ../../apps/hypridle/home.nix
-    ../../apps/hyprlock/home.nix
-    ../../apps/walker/home.nix
-    # ../../apps/fsel/home.nix
-    ../../apps/hyprpaper/home.nix
-    ../../apps/hyprpaper/switch-wallpaper.nix
-    ../../apps/tte/home.nix
+    ../../apps/hyprland
+    ../../apps/hypridle
+    ../../apps/hyprlock
+    ../../apps/walker
+    # ../../apps/fsel
+    ../../apps/hyprpaper
+    ../../apps/tte
   ];
-}
+}