Add comprehensive documentation with JSDoc comments and contributing guidelines

[Copilot]

This PR addresses the lack of documentation for newcomers by implementing comprehensive documentation improvements across the ICPC Platform project.

Changes Made

JSDoc Comments for Action Functions

Added detailed JSDoc documentation to all major action functions including:

• API Route Handlers: Complete documentation for authentication (/api/auth/login, /api/auth/register) and training management (/api/training) endpoints with parameter descriptions, response examples, and error handling details
• Utility Functions: Session management (encryptSession, decryptSession), email service (sendEmail), CSS utilities (cn), and database cleanup functions
• React Components: Page components (TrainingsPage, CreateTrainingPage) and UI components (TrainingCard) with prop interfaces and usage examples

Example of the added documentation:

/**
 * Handles user login authentication
 * 
 * @param request - The incoming HTTP request containing login credentials
 * @returns A NextResponse with authentication status and session cookie
 * 
 * @description
 * Authenticates a user by validating their username and password against the database.
 * On successful authentication, creates an encrypted session cookie and returns it.
 */
export async function POST(request: NextRequest) {
  // Implementation...
}

Enhanced README with Getting Started Guide

Completely rewrote the placeholder sections with:

• Prerequisites: Node.js, PostgreSQL, and Git requirements with download links
• Installation Steps: Complete setup process from cloning to running the development server
• Environment Configuration: Detailed .env.local template with all required variables
• Database Setup: Step-by-step database creation, migration, and seeding instructions
• Learning Resources: Curated links to Next.js, TypeScript, Drizzle ORM, Tailwind CSS, and competitive programming resources
• Development Workflow: Daily development process, useful commands, and development tools

Comprehensive Contributing Guide

Created a detailed CONTRIBUTING.md (12,000+ characters) covering:

• Project Architecture: In-depth explanation of the Next.js App Router structure, file organization, and routing conventions
• Development Guidelines: Branch naming conventions, commit message standards, and pull request workflow
• Code Standards: TypeScript best practices, React component guidelines, and file naming conventions
• API Development: Route handler patterns, input validation with Zod, and error handling standards
• Database Guidelines: Schema design principles and query best practices with Drizzle ORM
• UI/UX Standards: Component design, accessibility, and styling approaches with Tailwind CSS

API Documentation

Added comprehensive API documentation at src/app/api/README.md including:

• Complete endpoint reference with request/response schemas
• Authentication requirements and session management
• Error response formats and status codes
• Testing instructions using the existing .rest files

Impact

This documentation improvement provides:

• Clear onboarding path for new contributors with step-by-step setup instructions
• Self-documenting codebase through comprehensive JSDoc comments on all action functions
• Development standards that ensure consistent code quality and contribution patterns
• API reference for frontend developers and external integrators

The codebase is now self-explanatory with guidance for newcomers, addressing the core issues identified in the original problem statement.

Fixes #110.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• fonts.googleapis.com
  • Triggering command: /usr/local/bin/node /home/REDACTED/work/icpc-platform/icpc-platform/node_modules/next/dist/compiled/jest-worker/processChild.js (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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