Added <ImageWithFallback> — a drop-in <img> that shows a subtle placeholder
(skate emoji or a caller-supplied icon) instead of the browser's broken-image
glyph when a user-supplied URL is missing or 404s. Fills the same layout box so
nothing shifts.
Swapped it into the content-image surfaces that display user-uploaded URLs:
- Marketplace item cards (grid + purchase dialog)
- Spot detail (hero + gallery thumbs) and map list/popup cards
- Shop detail (hero + gallery)
- Crew & Lab cross-link cards (icon fallback)
- Crew agent panel, newsletter issue view + notification bell newsletter thumb
- Stash gear cards (list + grid), profile banner (NIP19), newsletter spot cards
Left untouched: avatars (shadcn Avatar already has fallbacks), QR codes and
rider-card/print images (data URLs, never 404), and in-form upload previews
(local object URLs).
Co-authored-by: shakespeare.diy <assistant@shakespeare.diy>
