Closes #568

Description

This PR addresses backend consistency for error payloads by ensuring that all structured validation (422) and server error responses (HTTPException and manual JSONResponses) include the current request ID.

Key changes include:

• Global Exception Handlers: Registered handlers for RequestValidationError and StarletteHTTPException in backend/secuscan/main.py. This ensures that all unhandled HTTP and request validation exceptions return request_id top-level alongside detail.
• Manual Error Responses: Added request_id to the manual JSONResponse constructed in _report_generation_error_response inside backend/secuscan/routes.py.
• Windows Host Support:
  • Fixed test_key_file_permissions in testing/backend/unit/test_api_auth.py by making the permission assertion platform-aware (chmod behaves differently on Windows).
  • Added a pytest_sessionfinish hook in testing/backend/conftest.py to forcefully terminate pytest at exit status, preventing event loop/thread hangs on Windows hosts.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

How Has This Been Tested?

We verified these changes by running the full unit test suite on a Windows host.

• Executed the command: python -m pytest testing/backend/unit
• All 696 tests passed successfully, including the newly added regression test suite covering:
  • Validation error payload request_id mapping.
  • HTTPException payload request_id mapping.
  • 500 report generation payload request_id mapping.
  • Client-supplied X-Request-ID round-trip verification.

Checklist

• My code follows the code style of this project.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.