[Michel (md-info)]

When pytest-base-url is absent, requesting the fallback base_url fixture on pytest 9.2 emits PytestRemovedIn10Warning. Projects treating this warning as an error cannot set up the page fixture.

Make the fallback fixture a static method in both the sync and async plugins. Extend the existing base URL tests to treat this specific warning as an error, preserving coverage for command-line, ini, environment, and unset values without failing on unrelated plugin warnings.

Fixes #341.

Validation:

• Python 3.12, pytest 9.2.0, Playwright 1.64.1, pytest-asyncio 1.3.0, Chromium: all 8 targeted sync/async cases passed without pytest-base-url installed.
• Verified the option case in each plugin fails against the original implementation with the exact fixture deprecation warning.
• Black 24.10.0, Flake8 7.1.1, and git diff --check passed for the changed files.
• Mypy 1.13.0 reports the same 8 errors on both unchanged upstream and this patch in this environment.
• The full cross-platform suite was not run locally.