Add registration validation and more activities

[Luhfernanda]

This pull request introduces several enhancements to the school activities management system, including new activities, improved signup validation, and better participant display functionality. The changes span across backend logic, frontend rendering, and styling.

Backend changes:

• Added six new activities categorized as sports, artistic, and intellectual activities to the activities dictionary in src/app.py. Each activity includes a description, schedule, maximum participants, and initial participants.
• Updated the signup_for_activity function in src/app.py to validate that a student is not already signed up for an activity before adding them. This prevents duplicate signups.

Frontend changes:

• Enhanced the activity cards in src/static/app.js to include a formatted list of participants. If no participants are signed up, a message indicating "Nenhum inscrito ainda" (no participants yet) is displayed.

Styling changes:

• Added new CSS rules in src/static/styles.css to style the participants section in activity cards, including formatting for participant lists and messages for no participants.

[Copilot]

Pull Request Overview

This PR enhances the school activities management system by adding new activities, signing up validation to prevent duplicate registrations, and improved participant display in the frontend.

• Added six new activities in the backend with categorized details
• Updated the signup logic to check for duplicate registrations
• Enhanced the frontend activity cards with formatted participant lists and corresponding styling

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
src/static/styles.css	New CSS rules to style the participants section in activity cards
src/static/app.js	Updated activity cards HTML to include formatted participants info
src/app.py	Added new activities and duplicate signup validation in backend