feat: normalize non-standard DOCX/XLSX before parse

[EricNGOntos]

Summary

• Detect encrypted Office containers and known DOCX/XLSX variants (macro/template content types) after download, then convert variants to standard files before billing and parse.
• Reject encrypted files with a clear client error instead of wrapping them as an unknown worker failure.
• Record office_compat on job metadata when a conversion ran, for later debugging.

Test plan

• make check
• Focused unit + parse-task contract tests for variant conversion, encrypted rejection, and existing invalid DOCX/XLSX errors

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