Add rate limiting handling with automatic retry

[beaufour]

Summary

• Add FlickrRateLimitError exception for HTTP 429 responses
• Implement automatic retry with exponential backoff on rate limit errors
• Parse Retry-After header when available
• Add configurable retry settings via set_retry_config() and get_retry_config()
• Default: 3 retries, 1s base delay, 60s max delay

Usage

The retry behavior can be configured or disabled:

import flickr_api

# Disable retries (raise immediately on rate limit)
flickr_api.set_retry_config(max_retries=0)

# Custom retry settings
flickr_api.set_retry_config(max_retries=5, base_delay=2.0, max_delay=120.0)

# Check current settings
config = flickr_api.get_retry_config()

When rate limited and retries are exhausted, raises FlickrRateLimitError with:

• retry_after: Suggested wait time from server (or None)
• content: Error message content

Background

Flickr returns HTTP 429 when the API rate limit (~3600 requests/hour) is exceeded. Previously this was not handled, causing JSON parsing to fail or return unexpected errors. Now the library automatically retries with backoff, or raises a clear exception when limits are exceeded.

Test plan

• All 254 tests pass
• 17 new tests for rate limit handling
• flake8 passes

🤖 Generated with Claude Code