Stable public image URLs eliminate API proxies and resize overhead

Avatars and logos render from storage directly. Fixes broken images on public pages; eliminates unnecessary API calls.

What's New

Avatar, logo, and photo rendering now uses stable public URLs directly from storage instead of passing through API proxies. This fixes broken images on public pages like invitation acceptance (where org logos previously couldn't load without authentication) and improves performance by eliminating unnecessary API round-trips and on-the-fly image resizing.