Image bubbles previously used the raw filename as alt text, so a failed
asset load exposed the file name in the broken-image box. Add a reusable
BubbleImage that renders an empty alt and falls back to a neutral
placeholder (ImageOff icon) on error; use it in the album, image, and
image-with-text bubbles, and drop the filename from their aria-labels.
Also add a global ScrollToTop that resets the window on route change so
desktop navigation matches mobile (e.g. clicking a category card no
longer lands at the bottom of the new page). Hash navigations are skipped
so #post-<id> deep-link scrolling still works.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
