test : add unit tests for logging_utils JSONFormatter and RequestIDFilter

[tmdeveloper007]

Summary of What Needs to be Done:
backend/secuscan/logging_utils.py has partial test coverage: existing tests cover basic serialization and exception formatting, but several edge cases are untested. The JSONFormatter does not handle a missing request_id attribute gracefully in all paths, and the RequestIDFilter has untested behavior for the no-request-id case.

Changes that Need to be Made:

• Add testing/backend/unit/test_logging_utils_extended.py
• Test JSONFormatter.format when record lacks request_id attribute entirely
• Test JSONFormatter.format when record.request_id is None vs missing attribute
• Test RequestIDFilter.filter: sets record.request_id to get_request_id() result
• Test RequestIDFilter.filter when get_request_id returns None
• Test JSONFormatter with a record that has all fields populated (complete integration)
• Use monkeypatch to patch get_request_id for isolation

Impact that it would Provide:

• Ensures log output is always well-formed JSON even with unusual log records
• Validates request ID injection in multi-threaded logging scenarios
• Improves debuggability of production log output

Note: This task is being handled by tmdeveloper007 — please assign to that account when picking it up.