[FEATURE]: Debate Topic Library with Evidence Database

Hi Team,

DebateAI provides a strong platform for structured, real-time debates between users and AI.

To further strengthen its educational value, I would like to propose a new feature:

### Debate Topic Library with Evidence Database

Currently, users debate without access to a structured research or evidence system.
This feature would provide a centralized knowledge base to support stronger, more informed debates.

### Proposed Features:
- Curated debate topics by category (Politics, Tech, Ethics, etc.)
- Evidence cards with verified sources
- Bookmark/save evidence for later use
- AI-suggested evidence during debates
- Community-contributed evidence with voting
- Citation generator for academic debates

### Why this matters:
- Encourages research-based debating
- Improves argument quality
- Makes DebateAI more educational
- Helps beginners learn faster
- Builds a knowledge-driven community

### Technical Approach (High-Level)

The feature will include:
- MongoDB collections for Topics, Evidence, and User Saved Evidence
- REST APIs in Go for topic and evidence management
- AI-powered evidence suggestions using LLMs
- React components for browsing topics, saving evidence, and viewing citations

Database will store:
- Debate topics with categories
- Evidence cards with sources, URLs, and community votes
- User bookmarks

APIs:
- GET /api/topics
- GET /api/evidence/:topicId
- POST /api/evidence
- POST /api/evidence/:id/vote
- POST /api/users/save-evidence

AI will suggest evidence during debates based on live argument context.

This approach is modular, scalable, and aligns with the current DebateAI architecture.

@bhavik-mangla I would love to contribute to implementing this feature if it aligns with the project roadmap.

Best regards,
Riya Chandra