FAC-1936: add constants for tax, cancellation, and global invoice fields

[javorosas]

Summary

• add constants for tax fields (TaxFactor, IepsMode)
• add constants for cancellation (CancellationMotive, CancellationStatus)
• add constants for global invoice fields (GlobalPeriodicity, GlobalMonths, ExportCode)
• add status constants for common document flows (InvoiceStatus, ReceiptStatus)
• update TaxSystem with missing SAT codes and expand Taxability values
• add missing webhook event constant receipt.cancellation_status_updated

Validation

• dotnet build -nologo