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/overlay/usr/local/bin/bee-openbox-session

@@ -7,8 +7,12 @@ xset s off
 xset -dpms
 xset s noblank
 
-# Set desktop background: dark with amber tint matching web UI palette.
-xsetroot -solid '#12100a'
+# Set desktop background.
+if [ -f /usr/share/bee/wallpaper.png ]; then
+    feh --bg-fill /usr/share/bee/wallpaper.png
+else
+    xsetroot -solid '#000000'
+fi
 
 tint2 &