fix: code review fixes

- Fix hardcoded user path in webapps.nix (use homeDirectory)
- Normalize wallpapers option to use .enable suffix
- Remove duplicate FZF keybind declaration
- Update comments to match actual implementation

home/desktop/theme/wallpapers.nix

@@ -5,9 +5,9 @@
   ...
 }:
 with lib; let
-  cfg = config.desktop.theme.wallpapers;
+  cfg = config.desktop.theme.wallpapers.enable;
 in {
-  options.desktop.theme.wallpapers = mkEnableOption "wallpapers for Hyprland";
+  options.desktop.theme.wallpapers.enable = mkEnableOption "wallpapers for Hyprland";
 
   config = mkIf cfg {
     xdg.configFile."hypr/wallpapers" = {