Update README to reflect actual project state

[Copilot]

README contained outdated project name, vague technology descriptions, and unclear implementation status. Updated to accurately document current CodeArena build.

Changes

Project Identity

• Corrected project name throughout (LeetLab → CodeArena)
• Updated repository URLs to Rahul5977/CodeArena

Technology Stack

• Added explicit versions: React 19, Vite 7.1, Tailwind CSS 4, Prisma 6.12, PostgreSQL 15, Redis 7, Socket.IO 4.8, Express 4.19
• Added missing dependencies: React Router 7, DaisyUI, Framer Motion, React Hook Form + Zod

Implementation Documentation

• Added comprehensive "Implemented Features" section covering:
  • Authentication & authorization (JWT + RBAC with 3 roles)
  • Code execution engine (Judge0 integration, 5 languages)
  • Problem management with full CRUD
  • Contest system with real-time leaderboards
  • DSA sheets with Razorpay payment integration
  • User playlists
  • Admin panel capabilities
  • Frontend features (Monaco Editor, theme toggle, split pane)
• Enhanced database schema with all 15+ models and relationships
• Added "Current Limitations" section for transparency (SMTP configured but unused, AI code review stub, partial admin UI)

Project Structure

• Expanded to show actual controllers, routes, and 40+ docs files
• Added references to existing test files (init-db.sql, test-sheets.sql, etc.)
• Included Judge0 language IDs for testing

Before:

- **React 18** - Modern React with hooks and context
- **Vite** - Fast build tool and dev server

After:

- **React 19** - Latest React with hooks and context
- **Vite 7.1** - Lightning-fast build tool and dev server
- **React Router 7** - Client-side routing
- **React Hook Form + Zod** - Form validation and management

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