Fix XLSX formula alignment for offset ranges

[hewliyang]

Summary

• account for non-zero calamine range starts when pairing XLSX cells with formulas and metadata
• use the explicit uncached-formula flag when deciding whether to invoke formula backfill
• add a regression test for a worksheet whose populated range starts below A1

Testing

• DEVELOPER_DIR=/Applications/Xcode.app/Contents/Developer cargo test --locked

This fixes cases where cached formula values were incorrectly treated as missing, causing unnecessary and very slow formula graph construction on workbooks with offset ranges.