feat: add pagination to miner PRs and issues endpoints

[Kelvinchen03]

Summary

Implements cursor-based pagination with hard result caps for the /miners/:githubId/pulls and /miners/:githubId/issues endpoints. Adds cursor and limit query parameters to prevent unbounded responses while maintaining backward compatibility. Results default to 50 per page with a maximum cap of 200.

Related Issues

Closes #100

Type of Change

• Bug fix
• New feature
• Refactor
• Documentation
• Other (describe below)

Testing

1. Started dev server: npm run dev in d:/Projects/gittensor/das-github-mirror/packages/das

2. Tested first page: GET /api/v1/miners/:githubId/pulls?limit=10

• Returns ≤10 results with next_cursor field

3. Tested pagination: GET /api/v1/miners/:githubId/pulls?cursor=&limit=10

• No duplicate results between pages

• Proper ordering by created_at DESC

4. Tested limit cap: GET /api/v1/miners/:githubId/pulls?limit=500

• Returns max 200 results (hard cap enforced)

5. Tested backward compatibility: GET /api/v1/miners/:githubId/pulls

• Works without pagination params, returns first 50 results

6. Ran automated test script: node test-pagination.js

• All pagination scenarios pass

Checklist

• I have read the Contributing Guide
• Code builds without errors
• New and existing tests pass (if applicable)
• Documentation updated (if applicable)
• No unnecessary dependencies added