ci(test): add Swagger endpoint tests workflow & runner; integrate into `test.sh`; refine OpenAPI request annotations

[Ludy87]

Description of Changes

• CI workflow: Introduces Swagger Endpoint Tests GitHub Actions workflow with a tag matrix, hardened runner, Java/Gradle/Python setup, app build/start, readiness wait on /v1/api-docs, and test execution via the new runner.
• Integration test runner: Adds testing/swagger_endpoint_test.py to exercise OpenAPI endpoints with parallelism, retries, strict/lenient mode, tag/path filters, dynamic request generation (JSON, multipart, form, binary), and sensible skips. Includes file-type heuristics for sample uploads (PDF, images, CBZ/CBR, certs).
• Sample assets for CI: Adds representative fixtures (sample.cbz, sample.cbr, chaptered PDF, README PDF, markdown) to support upload endpoints.
• Hook maintenance: Bumps pre-commit hooks:
  • ruff-pre-commit from v0.12.7 → v0.13.3
  • pre-commit-hooks from v5.0.0 → v6.0.0
• Local test pipeline: Extends testing/test.sh to run Swagger endpoint tests against a local instance.
• OpenAPI accuracy & DX:
  • Adds/updates request body metadata (e.g., contentMediaType, format, explicit application/pdf) for CBZ/CBR and PDF converters.
  • Sets a default value for redaction padding for clearer docs and generated clients.
  • Expands ConvertWebsiteToPDF controller consumes to also accept application/x-www-form-urlencoded.
  • Documents 500 response for Admin Settings retrieval endpoint.

Why the change was made

• Increase confidence that documented endpoints are live and behave as described (contract tests against the OpenAPI spec).
• Catch regressions early in CI with fast feedback and actionable logs.
• Improve client generation fidelity by enriching schema annotations and defaults.
• Provide deterministic sample data for upload-heavy endpoints.
• Harden CI runners and make the suite reproducible locally and in CI.

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Checklist

General

• [x] I have read the Contribution Guidelines
• [x] I have read the Stirling-PDF Developer Guide (if applicable)
• [ ] I have read the How to add new languages to Stirling-PDF (if applicable)
• [x] I have performed a self-review of my own code
• [x] My changes generate no new warnings

Documentation

• [ ] I have updated relevant docs on Stirling-PDF's doc repo (if functionality has heavily changed)
• [ ] I have read the section Add New Translation Tags (for new translation tags only)

UI Changes (if applicable)

• [ ] Screenshots or videos demonstrating the UI changes are attached (e.g., as comments or direct attachments in the PR)

Testing (if applicable)

• [ ] I have tested my changes locally. Refer to the Testing Guide for more details.

[Frooodle]

will merge after build passes again, prob need to add to our docs somewhere about this needing to get updated for new endpoints etc

[Ludy87]

/prdeploy

[stirlingbot[bot]]

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