feat: fix XML element ordering and add totalTributosPercentual fields

[vitormattos]

Summary

• DpsData: add totalTributosPercentualFederal, totalTributosPercentualEstadual, totalTributosPercentualMunicipal string fields to carry estimated tax percentages from settings into the DPS payload.
• XmlBuilder: fix element ordering to match SEFIN validator expectations — tpAmb, dhEmi, verAplic, serie, nDPS, dCompet, tpEmit, cLocEmi now precede prest; extract buildServico() and buildValores() methods; replace cMun with cLocEmi (only cLocEmi required by schema); add conditional trib block with tribMun, tribFederal, and totTrib sub-elements.
• Tests: update XmlBuilder tests to assert the new element order and methods; fix NfseClient test to assert cLocEmi instead of the removed cMun element.

Related

Module counterpart tracked in LibreCodeCoop/akaunting-nfse.