Underground FX Master Rebuild Fresh v2

This pack is a genuine fresh-shell rebuild using the existing site as a content/function source.

What changed:
- Bootstrap 5 shell added to public and admin pages
- New shared design system in assets/css/ugfx-master.css
- New shared public shell in includes/public_bootstrap.php
- New shared admin shell in admin/includes/admin_bootstrap.php
- Home, About, DJs, Schedule, News, Events, Contact, Chat, Requests rebuilt into the new shell
- Stream target updated to http://radio.undergroundfxradio.com:9000/stream
- News and events pages now render media cards directly
- DJ page reads from the source roster JSON

Still to do before final live deployment:
- reconnect deeper admin tools into the new admin shell one by one
- hard-test now playing endpoint against live server
- final wording sweep on every legacy admin subpage
- exact DJ roster audit against live source if required