Fix black desktop and Chromium blank page on startup

- Set xsetroot solid background (#12100a, dark amber) so openbox
  doesn't show bare black before Chromium opens
- Re-add healthz wait loop before launching Chromium: without it
  Chromium opens localhost/loading before bee-web is up and gets
  connection-refused which renders as a blank white page

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

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

@@ -7,8 +7,21 @@ xset s off
 xset -dpms
 xset s noblank
 
+# Set desktop background: dark with amber tint matching web UI palette.
+xsetroot -solid '#12100a'
+
 tint2 &
 
+# Wait up to 60s for bee-web before opening Chromium.
+# Without this Chromium gets connection-refused and shows a blank page.
+_i=0
+while [ $_i -lt 60 ]; do
+    curl -sf http://localhost/healthz >/dev/null 2>&1 && break
+    sleep 1
+    _i=$((_i+1))
+done
+unset _i
+
 chromium \
     --disable-infobars \
     --disable-translate \