[dav3exe]

Brings startnextgen/startng-be up to date with the Cybertron-HNG fork's main (10 commits). Each change went through a PR into the fork's dev with pytest and malware-scan green, then dev into main (#136) with CodeQL, Analyze and the dependency checks green as well.

• Rooms: rematch (Hamzat, #133): after a game ends, players can play again in the same room, with the seats moved round so the other player goes first. A bot always agrees. Quiz and bingo go back to waiting for the host.
• Rooms: chess (Hamzat, #134): our own rules code with no chess library (castling, en passant, promotion, check, checkmate, stalemate, and automatic draws) and a bot. Bot moves run off the event loop. It is only used by games that ask for chess rooms, and rooms stay off until rooms is in FEATURES.
• Game pages (Chloe, #137): about, how to play, FAQ and walkthrough pages get a hero with the cover, tabs, a facts row, section cards, key caps and a FAQ whose questions open and close. The words and the search-engine data are unchanged; only the wrapping elements changed.
• Categories (Chloe, #135): a game's page no longer lists the search-word categories ("Web games", "Browser games", "Free online games", "HTML5 games") as chips. They are on every game, so they say nothing about it. Their own pages stay.

To deploy: no new settings and no migrations. Deploy together with startnextgen/startng-fe: the game pages' new markup looks unstyled without the matching styles, and the rematch button is ignored until this is live.

Checks run locally on dev (the exact code in this PR): pytest 1000 passed, 2 skipped.