Add registration validation and more activities

[plumass]

This pull request adds several new activities to the system, improves the signup logic to prevent duplicate registrations, and enhances the user interface by displaying participant lists for each activity. The changes are organized into backend data/model updates, backend logic improvements, and frontend display enhancements.

Backend data/model updates:

• Added new activities to the activities dictionary in src/app.py, including sports (Soccer Team, Basketball Club), artistic (Art Workshop, Drama Club), and intellectual (Mathletes, Science Club) activities, each with their own schedule, participant list, and maximum capacity.

Backend logic improvements:

• Updated the signup_for_activity function in src/app.py to prevent users from signing up for the same activity more than once by checking if the email is already in the participant list and raising an error if so.

Frontend display enhancements:

• Modified src/static/app.js to show a list of participants for each activity card, including a message when there are no participants yet.
• Added new CSS styles in src/static/styles.css to visually enhance the participant list section in activity cards, including spacing, colors, and hover effects.

[Copilot]

Pull Request Overview

This pull request enhances the activity management system by adding new activities, implementing duplicate registration prevention, and displaying participant lists on the frontend. The changes improve both user experience and data integrity by preventing duplicate signups and providing better visibility into activity participation.

• Added six new activities across sports, artistic, and intellectual categories with predefined participants
• Implemented backend validation to prevent duplicate registrations for the same activity
• Enhanced the frontend to display participant lists for each activity with styling

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/app.py	Added new activities and duplicate registration validation logic
src/static/app.js	Updated UI to display participant lists for each activity
src/static/styles.css	Added CSS styling for the new participant list display

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[Copilot]

The text 'Aucun participant pour le moment' is in French, which appears inconsistent with the rest of the application that uses English. Consider changing to 'No participants yet' for consistency.

Suggested change

	? '<li><em>Aucun participant pour le moment</em></li>'
	? '<li><em>No participants yet</em></li>'

[Copilot]

There's trailing whitespace at the end of this line. Consider removing it for cleaner code formatting.

Suggested change

	raise HTTPException(status_code=400, detail="Already signed up for this activity")
	raise HTTPException(status_code=400, detail="Already signed up for this activity")