Missing Integration Coverage for Toolforge/Commons sync lifecycles

[ayushshukla1807]

Problem:
Testing coverage is currently heavily weighted toward basic SQLAlchemy session fixtures. However, there is zero mock-based coverage for the loaders.py and Wikimedia Commons API sync interactions.

Impact:
If Commons changes its API schema or a category tree redirects, the import_entries function can silently fail or skip files without the CI/CD pipeline catching it.

Proposed Solution:
Introduce pytest-mock or responses fixtures to explicitly mock https://montage.toolforge.org/ and the Wikimedia API. We specifically need integration checks testing how the system handles <redirect> nodes and HTTP 429 Rate Limits during large CSV imports.