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/apps-optional.nix

@@ -1,6 +1,6 @@
 {
   imports = [
-    ../../apps/btop/home.nix
-    ../../apps/jellyfin/home.nix
+    ../../apps/btop
+    ../../apps/jellyfin
   ];
 }

modules/home/apps.nix

@@ -1,8 +1,8 @@
 {
   imports = [
-    ../../apps/yazi/home.nix
-    ../../apps/gemini/home.nix
-    ../../apps/firefox/home.nix
-    # ../../apps/starship/home.nix
+    ../../apps/yazi
+    ../../apps/gemini
+    ../../apps/firefox
+    # ../../apps/starship
   ];
 }

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
   ];
-}
+}

modules/home/music.nix

@@ -24,8 +24,8 @@
   '';
 in {
   imports = [
-    ../../apps/jellyfin-tui/home.nix
-    ../../apps/cava/home.nix
+    ../../apps/jellyfin-tui
+    ../../apps/cava
   ];
   home.packages = [
     launch-music

modules/home/terminal.nix

@@ -1,10 +1,10 @@
 {
   imports = [
-    ../../apps/neovim/neovim.nix
-    ../../apps/git/home.nix
-    ../../apps/zoxide/home.nix
-    ../../apps/fish/home.nix
-    ../../apps/ghostty/home.nix
-    ../../apps/fastfetch/home.nix
+    ../../apps/neovim
+    ../../apps/git
+    ../../apps/zoxide
+    ../../apps/fish
+    ../../apps/ghostty
+    ../../apps/fastfetch
   ];
 }

modules/home/theme.nix

@@ -1,6 +1,6 @@
 {
   imports = [
-    ../../apps/stylix/home.nix
-    ../../apps/matugen/home.nix
+    ../../apps/stylix
+    ../../apps/matugen
   ];
 }

modules/home/waybar.nix

@@ -1,6 +1,5 @@
 {
   imports = [
-    ../../apps/waybar/home.nix
-    ../../apps/waybar/hakase-popup.nix
+    ../../apps/waybar
   ];
-}
+}