Add new research sources

[benevolentbandwidth-nurtekin]

Currently, Research Agent primarily relies on arXiv for paper ingestion.

As we scale categories and improve coverage, we want to explore integrating additional research sources.

Goal: Evaluate and integrate additional academic sources (API-based only) to enhance paper discovery and influence prediction.

Possible directions include:

1. Conference APIs
2. OpenReview
3. Domain-specific repositories
4. Other structured academic APIs

Key Considerations

1. Use official APIs only (no scraping)
2. Maintain data quality and deduplication
3. Ensure new sources integrate cleanly into the existing ranking pipeline
4. Preserve system performance and reliability