Add comprehensive badge system and enhanced submission feedback

feat: Add AI chatbot, enhance learning paths, and update README

fix: resolve 'paths.find is not a function' bug in StudentLearningPath & StudentAnalytics

feat: ML-powered personalized learning paths with visual roadmap, topic-wise resources, and teacher analytics view

Save point: RAG integration, dashboards, auto-eval, grading UI - before ML learning path overhaul

Integrate RAG-based question generator: upload PDF, select topic/type/count, generate questions from document content

Add README with setup instructions and requirements.txt for ML service

Add ml_service folder - Python ML service with FastAPI

Add client folder - React frontend with components and contexts

Add server folder - Express.js backend with APIs and Models

Add .gitignore