refactor config with better structure

home/config/default.nix

@@ -1,28 +0,0 @@
-{ ... }:
-{
-  xdg.configFile."niri" = {
-    force = true;
-    recursive = true;
-    source = ./niri;
-  };
-  xdg.configFile."alacritty" = {
-    force = true;
-    recursive = true;
-    source = ./alacritty;
-  };
-  xdg.configFile."fuzzel" = {
-    force = true;
-    recursive = true;
-    source = ./fuzzel;
-  };
-  # Shared with SDDM (nixos/dm/sddm.nix); niri loads it from this path.
-  home.file."Pictures/Wallpapers/wallpaper.png" = {
-    force = true;
-    source = ../../assets/wallpaper.png;
-  };
-  xdg.configFile."helix" = {
-    force = true;
-    recursive = true;
-    source = ./helix;
-  };
-}

home/config/niri/env.kdl

@@ -44,9 +44,6 @@ environment {
     // Clutter: Force Wayland backend.
     CLUTTER_BACKEND "wayland"
 
-    // Firefox: Force native Wayland rendering (massively improves scrolling smoothness).
-    MOZ_ENABLE_WAYLAND "1"
-
     // Electron/Chromium: Automatically flags apps (VS Code, Discord, Obsidian) to use Wayland.
     ELECTRON_OZONE_PLATFORM_HINT "auto"