Use `import infra.local_converter as lc_mod` consistently instead of mixing `import` and `from ... import` for the same module. Addresses CodeQL review comment on PR #58.
25 tests covering all backend robustness fixes: - TestClassifyError (9): user-friendly error message mapping - TestDefaultTableMode (4): settings.default_table_mode injection - TestDocumentTimeout (2): document_timeout wired into pipeline - TestConverterLockTimeout (3): lock timeout + release guarantees - TestConvertSyncLimits (4): max_num_pages/max_file_size forwarding - TestGetDefaultConverterReset (3): converter singleton reset on failure Ref #57
