icon_url systematically missing in all frontend types

## Warning Backend includes icon_url: str|None on OrganizationProfile, GroupDetail, and UserProfile, but no frontend type declares this field. ## Impact If icon_url is intended for use (e.g., favicon-sized icons for tabs, bookmarks, or compact UI), the frontend silently drops it. If it is unused, it should be removed from the backend schemas to reduce confusion. ## Decision Needed Either adopt icon_url in the frontend or remove it from backend schemas. ## Found by API contract audit (2026-03-19)