Add AI-powered Smart Study Planner

[Bhavika-0308]

Overview

This PR introduces the AI-powered Smart Study Planner feature, allowing users to automatically extract tasks from unstructured text and generate customized study schedules.

Key Features & Changes

• AI Task Extraction (Gemini API): Users can now paste syllabus text or loose notes, and the system automatically extracts tasks, deadlines, and priorities using Google's Gemini 2.5 Flash model.
• NLP Heuristic Fallback: Added a robust local Natural Language Processing fallback parser that handles task extraction if the API key is not configured or offline.
• Smart Study Schedule Generation: Added a feature to auto-generate a 3-day customized study schedule (balancing learning and revision sessions) based on current tasks, exams, goals, and weak subjects.
• New UI/UX:
  • Added planner.css and planner.js for the new study planner interface.
  • Added dynamic celebration animations using confetti.browser.min.js.
• Backend Updates:
  • Updated server.js with new REST endpoints (/api/planner/generate and /api/extract).
  • Updated SQLite database initializations in database.js for robust task and session tracking.
  • Added environment variable configuration (.env.example) to securely manage API keys.

Testing Performed

• Verified server starts successfully and falls back to local NLP when GEMINI_API_KEY is missing.
• Verified Gemini API integration accurately extracts deadlines, subjects, and priorities from raw text.
• Ensured safe handling of environment variables (added .env to .gitignore).