[FEATURE] Add WebVTT regression test coverage

[Rahul-2k4]

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Summary

• Add regression test for WebVTT output format (-out=webvtt)
• Create golden file sample1.webvtt for test validation
• Add "Output Formats" category for format-specific tests
• Document golden file provenance for reproducibility

Test plan

• CI passes on all Python versions (3.10, 3.12, 3.13, 3.14)
• WebVTT test correctly validates header-only output

[Rahul-2k4]

Hi @canihavesomecoffee ,
Thanks for the clarification. I’ve moved the WebVTT category, regression test, and golden output registration into an Alembic migration so they’re applied to running instances via flask db upgrade, not just during install. The golden output is stored DB-side, and the category/test linkage is now explicit through regression_test_category, so existing deployments are covered.
Please let me know if you’d like me to also tighten or verify the fresh-install path.

[sonarqubecloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud