Add wallpaper: black background with amber EASY-BEE ASCII art logo

- Add feh and python3-pil to package list
- Add chroot hook that generates /usr/share/bee/wallpaper.png using PIL:
  black background, EASY-BEE box-drawing logo in amber (#f6c90e),
  "Hardware Audit LiveCD" subtitle in dim amber — matches motd exactly
- bee-openbox-session: set wallpaper with feh --bg-fill, fall back to
  xsetroot -solid black if wallpaper not found

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

iso/builder/config/package-lists/bee.list.chroot

@@ -60,6 +60,8 @@ qrencode
 # Local desktop (openbox + chromium kiosk)
 openbox
 tint2
+feh
+python3-pil
 xorg
 xterm
 chromium