test: add reproducible domain table generator

[vitormattos]

Completes the remaining Definition of Done for #51.

Summary

• add a dependency-free Python XLSX normalizer for official annexes A/B/C
• generate the committed municipality/country/service/NBS/operation-indicator TSV snapshots directly from XLSX
• honor spreadsheet cell references and vertically merged cells
• reject unexpected official cardinalities instead of silently accepting partial data
• add --check mode for byte-for-byte snapshot verification
• add a network-free synthetic workbook test and dedicated CI job

The generator is a development/update tool only; runtime remains fully offline and PHP-only.

If CI passes, #51 can be closed without weakening its reproducibility requirement.