fix: missed base_url for ai_scrape url.

[Khurdhula-Harshavardhan]

This pull request updates the package version and modernizes Python compatibility requirements, while also improving test configuration for API usage. The most important changes are grouped below by theme.

Version and Compatibility Updates:

• Bumped the package version from 0.3.8 to 0.3.9 in both jigsawstack/version.py and setup.py. [1] [2]
• Updated the minimum required Python version from 3.7 to 3.9 in setup.py, and removed support for Python 3.7 and 3.8 in the classifiers, adding support for Python 3.12. [1] [2]

Test Configuration Improvements:

• Modified the instantiation of JigsawStack and AsyncJigsawStack in tests/test_ai_scrape.py to use a configurable base_url and custom headers, improving flexibility and cache control in tests.
• Minor formatting update for cookie parameters in test configuration for better readability.