Add registration validation and more activities

[sofiar-msft]

This pull request introduces enhancements to the activity management system by adding new activities, improving validation for participant signup, and updating the UI to display participant information. Additionally, it includes styling updates for better visual presentation of participant details.

Backend Changes:

• New Activities Added: Introduced multiple new activities categorized under sports, artistic, and intellectual themes, each with descriptions, schedules, maximum participant limits, and initial participants. (src/app.py, src/app.pyR41-R79)
• Signup Validation: Added validation to prevent duplicate participant signups for the same activity, raising an HTTP exception if a student is already signed up. (src/app.py, src/app.pyR104-R107)

Frontend Changes:

• Participant Information Display: Enhanced activity cards to display participant details, including a list of participants or a message indicating no participants yet. (src/static/app.js, src/static/app.jsL25-R35)
• Styling for Participant Section: Added CSS styles for the participant section, including background color, padding, and improved list formatting for participant names. (src/static/styles.css, src/static/styles.cssR145-R167)

[Copilot]

Pull Request Overview

This PR expands the set of activities, adds a check to prevent duplicate signups, and updates the UI to list participants with accompanying styles.

• Introduces sports, artistic, and intellectual activities in the backend
• Adds signup validation to reject duplicate participant registrations
• Enhances frontend cards to display participant lists and applies new CSS for 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 a duplicate-signup validation in signup_for_activity
src/static/app.js	Updated activity card markup to include a participants section and relabeled fields
src/static/styles.css	Added styles for .participants-section and .participants-list

Comments suppressed due to low confidence (1)

src/app.py:105

• Consider adding a test case to cover the duplicate signup validation path, ensuring the HTTP 400 error is thrown as expected.

    if email in activity["participants"]:

[Copilot]

Rendering participant names directly via innerHTML opens a risk for XSS if the data isn't sanitized. Consider using DOM methods or sanitizing input before insertion.

Suggested change

	? details.participants.map(p => `<li>${p}</li>`).join('')
	: '<li><em>No participants yet</em></li>'}
	? (() => {
	const participantsList = document.createDocumentFragment();
	details.participants.forEach(p => {
	const listItem = document.createElement("li");
	listItem.textContent = p;
	participantsList.appendChild(listItem);
	});
	return participantsList;
	})()
	: (() => {
	const noParticipantsItem = document.createElement("li");
	noParticipantsItem.innerHTML = "<em>No participants yet</em>";
	return noParticipantsItem.outerHTML;
	})()}

[Copilot]

[nitpick] Previously the UI displayed available spots; consider also computing and showing remaining slots (max_participants minus current participants) to maintain consistency in availability info.

Suggested change

	<p><strong>Max Participants:</strong> ${details.max_participants}</p>
	<p><strong>Max Participants:</strong> ${details.max_participants}</p>
	<p><strong>Remaining Slots:</strong> ${spotsLeft}</p>