MDW Admin Branding + Updater Completion Patch

Updates:
- Adds the shared Murdock DevWorks website logo to the MDW Admin header.
- Changes document letterheads to use the same shared website logo asset.
- Removes the separate MDW document-logo block from generated documents.
- Adds a clear updater completion message with counts and timestamp after Apply Update.
- Keeps protected paths untouched.

Files updated:
- devworks-admin/lib/functions.php
- devworks-admin/lib/document-render.php
- devworks-admin/assets/admin.css
- devworks-admin/updater.php

Requires existing logo asset:
- images/branding/murdock-devworks-logo-header.png
