Issue 124 add event link to individual game page

[bilibilistack]

Change Summary

#124
This pull request introduces improvements to how game events are displayed and fetched on the individual game page. The main changes include dynamically fetching event data for each game, updating the event display logic, and enhancing the backend to restrict access to unpublished events.

In case no events or unpublished:

Frontend: Event integration and display

• Added the useEvent hook to fetch event data based on the game's associated event, replacing the previous hardcoded event placeholder. (client/src/pages/games/[id].tsxR8, client/src/pages/games/[id].tsxR21-R23)
• Updated the event display api to show the event name as a link if available, or a fallback message if not, improving user experience and accuracy. (client/src/pages/games/[id].tsxR62-R63, client/src/pages/games/[id].tsxL68-L69, client/src/pages/games/[id].tsxL176-R193)

Backend: Event access control

• Modified the EventDetailAPIView to only allow access to events that have been published (i.e., their publicationDate is not in the future), and to return a clear error message if the event is unpublished or does not exist.

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Related issue

• Resolve Add event link to individual game page #124