feat: implement GitHub API rate limiting with smart backoff

[ghinks]

Summary

Implements intelligent GitHub API rate limiting to prevent hitting API limits while maintaining optimal performance.

Key Features

• ✅ Smart backoff logic - Monitors X-RateLimit-Remaining and X-RateLimit-Reset headers
• ✅ Configurable thresholds - 10 request buffer with minimum 60-second sleep
• ✅ Dual implementation - Async for get_reviewers_rest.py and sync for get_prs.py
• ✅ Robust error handling - Gracefully handles missing or invalid headers
• ✅ Informative logging - Shows remaining requests and sleep duration
• ✅ Header compatibility - Supports both hyphenated and underscore variations

Implementation Details

Async Rate Limiting (get_reviewers_rest.py)

• check_rate_limit_and_sleep() function integrated into fetch operations
• Sleeps until rate limit reset when remaining requests ≤ 10
• Uses asyncio.sleep() for non-blocking operation

Sync Rate Limiting (get_prs.py)

• backoff_if_ratelimited() function called after each API response
• Calculates sleep time based on reset timestamp with 5-second buffer
• Uses time.sleep() for synchronous operation

Testing

• ✅ All 60 tests pass
• ✅ MyPy type checking passes
• ✅ Ruff linting clean
• ✅ No functionality broken

Example Behavior

GitHub API rate limit approaching. Remaining: 8, sleeping for 245 seconds.

🤖 Generated with Claude Code