new_bot_game starts a game against the bot at the chosen level and ends the
search for an opponent. BotPlayer works out the bot's moves on its own thread
pool and plays them on the game loop after the previous move's animation and a
thinking time. Bot games keep their settings across restarts.
The Quarkus project moves to apps/backend and the Express sources go.
The image is built from the repo root as before, with Temurin 25, and
runs as a non-root user on port 6000. Compose passes the database as a
JDBC URL with the same MANCALA_DB_PASSWORD.
