bsp-cli: drop stale chromium rescue block + orphaned desktop blobs

Three lines in armbian-bsp-cli's postinst:

  if [[ -L "/usr/lib/chromium-browser/master_preferences.dpkg-dist" ]]; then
      mv /usr/lib/chromium-browser/master_preferences.dpkg-dist /usr/lib/chromium-browser/master_preferences
  fi

shipped in 2018 (commit e7657a5) alongside
packages/bsp/common/usr/lib/chromium-browser/master_preferences.dpkg-dist,
as the tail half of a rescue pattern that dealt with chromium-browser's
conffile clashing with an armbian-supplied symlink/preseed file.
The ship-side half was removed long ago — bsp-cli no longer packages
anything under /usr/lib/chromium-browser/ — so the -L test is never
true on a fresh install. Dead code.

It's also the wrong architectural coupling in the new world:
chromium branding (master_preferences, policies, chromium.d flags)
lives in armbian-config as of the first commit in this PR
(configng:tools/modules/desktops/branding/browsers/etc/). bsp-cli
shouldn't be touching chromium at all.

Drop the dead rescue.

Also wipe packages/blobs/desktop/ wholesale. The entire subtree
(124 files, ~4000 lines: chromium.conf / firefox.conf / icons /
desktop-icons / desktop-splash / desktop-wallpapers / lightdm /
lightdm-wallpapers / sddm / skel / xorg.conf.cubox) was consumed
exclusively by the per-DE create_desktop_package.sh scripts under
config/desktop/, deleted in the first commit of this PR. No live
reference remains — grep -rln across lib/ config/ extensions/
packages/ returns zero hits for every path under
packages/blobs/desktop/.

Source of truth for desktop branding assets is now
configng:tools/modules/desktops/branding/ (wallpapers, greeters,
skel, browser policies).

Author: igorpecovnik

lib/functions/bsp/armbian-bsp-cli-deb.sh

@@ -460,10 +460,6 @@ function board_side_bsp_cli_postinst_finish() {
 		mv /etc/default/armbian-firstrun.dpkg-dist /etc/default/armbian-firstrun
 	fi
 
-	if [[ -L "/usr/lib/chromium-browser/master_preferences.dpkg-dist" ]]; then
-		mv /usr/lib/chromium-browser/master_preferences.dpkg-dist /usr/lib/chromium-browser/master_preferences
-	fi
-
 	# Reload services
 	systemctl --no-reload enable armbian-hardware-monitor.service armbian-hardware-optimize.service armbian-zram-config.service armbian-led-state.service > /dev/null 2>&1
 }