[WIP] Add expiration time feature for puzzle system

[Copilot]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

Add an "Expiration Time" feature for my Puzzle System:
When an admin set up a puzzle game using /puzzle-create, they can input an optional "expiration time" in the modal (10m, 3h, 5d, 2w, etc.), and the bot will record that in the database. When an admin activate a game using /puzzle-manage, the bot will schedule a task to inactivate the game after "expiration time"(use the time when admin activate the game as starting point). The admin can still manually inactivate the game using /puzzle-manage, and the bot will cancel the task. Also, the bot might restart during the period, so you need to come up with a solution to resume the task when the bot is being restarted (downtime may vary from long to short). And there are previously set games that do not have expiration time. The bot should ignore these games when doing related jobs. The bot should also ignore the games in which admin did not provide an expiration time.

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