Polish Waybar and add Bluetooth and walker service

Refactor Waybar config and CSS: add rgb/radius helpers and tweak
sizes, spacing, colors, tooltips, icons and transitions

Enable gtk-layer-shell and reload-on-change. Move exec-once into
settings and adjust modules and workspaces formatting

Add blueman and bluez to basic apps for Bluetooth support

Add elephant to home packages and add a systemd user service for
walker; change Hyprland exec-once to enable and start elephant.service

home/system/walker/default.nix

@@ -1,9 +1,29 @@
-{pkgs, ...}: {
+{ pkgs, ... }:
+
+{
   home.packages = with pkgs; [
     walker
+    elephant
   ];
 
+  systemd.user.services.walker = {
+    Unit = {
+      Description = "Walker application service";
+      After = [ "graphical-session.target" ];
+      PartOf = [ "graphical-session.target" ];
+    };
+
+    Service = {
+      ExecStart = "${pkgs.walker}/bin/walker --gapplication-service";
+      Restart = "on-failure";
+    };
+
+    Install = {
+      WantedBy = [ "graphical-session.target" ];
+    };
+  };
+
   wayland.windowManager.hyprland.settings.exec-once = [
-    "walker --gapplication-service"
+    "sh -lc 'elephant service enable && systemctl --user start elephant.service'"
   ];
-}
+}