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/base/cli-tools/fzf.nix

@@ -31,7 +31,6 @@ in {
         "--preview='bat --color=always -n {}'"
         "--bind 'ctrl-/:toggle-preview'"
         "--header 'Press CTRL-Y to copy command into clipboard'"
-        "--bind 'ctrl-/:toggle-preview'"
         "--bind 'ctrl-y:execute-silent(echo -n {2..} | wl-copy)+abort'"
       ];
       defaultCommand = "fd --type f --exclude .git --follow --hidden";