A hub for your format: community feed, rotation history, and admins

Every format now has its own hub page pulling together rotation history, participants, decks, matches, and stats in one place, instead of scattering that information across separate pages. Formats also gained a community feed: post messages, run polls, and share photos with everyone in the format — a lightweight way to talk shop without leaving TCGCore for a group chat elsewhere. Format owners can now also hand out an admin role to trusted members, so pool/banlist management doesn't have to sit with one person alone.