Improve student activity registration system

[Pollodiabolo]

This pull request introduces several enhancements to the activities management system, focusing on expanding available activities, improving participant management (including the ability to remove participants), updating the frontend to reflect these changes, and adding comprehensive tests. These changes collectively improve both user experience and code reliability.

Backend enhancements:

• Added several new activities to the activities data structure in src/app.py, each with its own description, schedule, participant capacity, and initial participants.
• Implemented a new API endpoint (DELETE /activities/{activity_name}/participants) to allow removal of a participant from an activity, with appropriate error handling if the participant or activity does not exist. Also added a check to prevent duplicate signups in the signup endpoint.

Frontend improvements:

• Updated the UI in src/static/app.js to display participants for each activity, including a delete button next to each participant for easy removal. The participants list is now styled for clarity, and activity selection is reset on refresh to avoid duplicate options. [1] [2]
• Added client-side logic to handle participant removal via the new API endpoint, with success/error feedback and automatic UI refresh. Also ensured the participants list updates after signups. [1] [2]

Testing and code quality:

• Introduced a pytest fixture in tests/conftest.py to ensure the in-memory activities data is restored after each test, maintaining test isolation.
• Added new tests in tests/test_activities.py to cover activity retrieval, successful and duplicate signups, and participant removal (both successful and not found scenarios).

[Copilot]

Pull request overview

This PR enhances the student activities system by expanding the in-memory activity catalog, preventing duplicate signups, adding participant removal support end-to-end (API + UI), and introducing pytest coverage to validate the new behaviors.

Changes:

• Expanded the activities dataset and added backend logic for duplicate signup prevention plus a new participant-removal endpoint.
• Updated the frontend to render participants per activity and allow removing participants via a delete button.
• Added pytest fixtures and tests to ensure isolation and cover GET, signup (including duplicates), and removal flows.

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/app.py	Adds new activities, prevents duplicate signups, and introduces DELETE /activities/{activity_name}/participants.
src/static/app.js	Renders participants and wires up delete-participant behavior; refreshes UI after signup/removal.
src/static/styles.css	Adds styling for participant lists and delete buttons.
tests/conftest.py	Introduces a fixture that snapshots/restores the in-memory activities dict per test.
tests/test_activities.py	Adds tests for activity retrieval, successful/duplicate signup, and participant removal scenarios.
requirements.txt	Adds test/dependency entries needed for running the new test suite.

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