Chat goes live, lobby gets cards

Added

• Chat connects to the server: global, party, and direct messages replace the mock data, with friends you can add by username.
• New players see recent global chat on join and can load older messages.
• Party chat is available inside a lobby.

Changed

• The lobby renders each seat as a playing card, with the host’s crown on the avatar and open seats dimmed and waiting.
• Lobby settings move into a modal, login or registration opens as an overlay, and Discord joins the social links.

Fixed

• Frontend asset changes reach the running server without a stale build.