point the B.U.G. page at a banner that exists

point the B.U.G. page at a banner that exists

bug.php asked for img/bug_bannerbig93.png, which is not in brisk-img: the
page came up with a broken image at the top. The repository carries
bug_bannerbig80.png (468x60) along with the mid and small variants, so
the 93 was renamed or dropped at some point without the page following.

Every image referenced from the js, php and css under web/ now answers
200, except img/probrisco.jpg, which sits inside a commented out rule in
dnd.css and is asked for by nobody.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Fseposbqj9mBbQXoT8KnBj