feat: Implement progress tracking and metrics system

[shettydev]

Priority: Low

The main goal is to build a progress tracking system that will monitor the users learning journey and provide meaningful metrics.

Requirements:

• Implement ProgressMetrics type from types.ts (added but not being used)
• Track learning streaks, time spent, and questions answered
• Monitor completed exploration paths and skill development
• Calculate the effectiveness of different Socratic techniques per user
• Provide progress visualization data
• Generate learning insights and recommendations

Acceptance Criteria
The whole idea is such that the user should be able to:

• See their learning progress over time
• View various learning metrics (accurately, otherwise it's pointless)\
• Be assured that their privacy is maintained for user data

Also, along with the analytics, other improvements:

• The progress data influences future question generation
• Metrics are available via API endpoints