Update dependencies and add Helium appimage

- Refresh many lock entries in flake.lock with new revisions and hashes.
- Enable the Helium appimage in default, desktop, and laptop host
  configs; add
  comment sections for web browsers and disable Fluxer by default.
- Rename the affinity option description from “Steam” to “Affinity”.
- Refactor appimage handling: introduce a generic mkAppImagePackage
  helper,
  import individual packages, and expose per‑package enable options.
- Update fluxer.nix to use a configurable icon size and adjust install
  paths.
- Bump Helium to version 0.12.3.1, update its hash, and make its icon
  size
  configurable.
- Adjust Hyprland settings: comment out the split‑layout bind, set
  configType = "hyprlang", enable Xwayland early, move vfr to the debug
  section, and comment out dwindle pseudotile.

modules/core/affinity.nix

@@ -5,7 +5,7 @@
   inputs,
   ...
 }: {
-  options.affinity.enable = lib.mkEnableOption "Steam";
+  options.affinity.enable = lib.mkEnableOption "Affinity";
 
   config = lib.mkIf config.affinity.enable {
     nixpkgs.overlays = [inputs.affinity-nix.overlays.default];