Add hot corners, media keys, orionshot, orionclip, notification history, autostart, GTK accent update, wallpaper slideshow, ISO build

- wm: hot corner polling via select()-based wm_run loop; TL=Exposé, TR=show desktop, BL=launcher, BR=lock
- wm: XF86 media key grabs (volume, brightness, playback) + Super+V for clipboard
- wm: autostart reads ~/.config/orionos/autostart on startup
- events: media key dispatch (amixer/brightnessctl/playerctl); Super+V → orionclip --show; Print → orionshot
- orionshot: new X11 screenshot tool, full-screen and rubber-band region modes, saves PNG to ~/Pictures/Screenshots/
- orionclip: new clipboard manager daemon; polls clipboard, stores 20 entries, popup via Super+V IPC
- orionnotify: append-only notification history log at ~/.local/share/orionos/notif-history.log
- themes: GTK accent updated from #3A6898 to #1E58A8 to match WM/deskbar
- themes: orionwallpaper gains --slideshow DIR [SECS] mode using feh + sleep loop
- iso: Docker-based archiso builder, live-session xinitrc, profiledef.sh
- Makefile: add orionshot and orionclip to all/clean/install; Docker-based iso target

iso/airootfs/root/.xinitrc

@@ -0,0 +1,2 @@
+#!/bin/bash
+source /etc/orionos/xinitrc