Devlog 1 — Draggable windows, terminal, and login screen

Built the main desktop environment for WebOS1. Windows can now be dragged around the desktop and bring themselves to the front when clicked (z-index). Added a custom login screen that asks for a username on startup, no passwords, just stored in memory for the session.
The big feature today was a working terminal app with a real shell-like prompt (username@webos:~$). It supports help, whoami, ls, pwd, clear, sudo (denial message for fun), apt install with animated fake install output, and neofetch showing system info.
Also replaced the default wallpaper with the classic Windows XP Bliss background and added custom SVG/icon assets for the desktop shortcuts.