fix: resolve Gemini API authentication and quiz generation

[nasseralkawari]

This PR resolves the issue where quiz generation was failing due to invalid or missing Gemini API credentials.

Problem

• Quiz generation endpoint (/api/quiz/generate) was returning:

  • 401 Unauthorized
  • GEMINI_API_KEY environment variable is not set

• Backend was unable to authenticate with the Gemini API

• Result: frontend showed "Failed to generate quiz"

Root Cause

• .env file was missing or incorrectly placed
• Invalid or unsupported API key was used
• Gemini API key was not properly loaded via environment variables

Fix Implemented

• Added proper .env configuration support using dotenv

• Ensured backend loads environment variables correctly:

  require('dotenv').config({ path: require('path').resolve(__dirname, '../.env') });

• Replaced invalid API key with a valid Gemini API key from Google AI Studio

• Restarted backend to apply environment changes

Additional Improvements

• Verified backend health endpoint (/api/quiz/health)
• Confirmed successful API response (200) from /generate
• Ensured frontend properly connects to backend (port 5000)

Testing

• Successfully generated quizzes from frontend

• Verified API response includes:

  • quizId
  • questions

• Confirmed no more authentication errors

Notes

• .env file is excluded from version control for security
• API keys must be configured locally for each developer

Impact

• Restores full quiz generation functionality
• Enables end-to-end flow (Generate → Quiz → Feedback → Dashboard)

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