Add \DocumentMetadata for PDF 2.0 / PDF/UA-2, load tagpdf with
activate-all, extend hypersetup with pdftitle/pdfauthor/pdflang/
pdfdisplaydoctitle, and add alt text to the letterhead and signature
images. Drop xetex-only xltxtra and switch the Makefile from xelatex
to lualatex. Verified compliant with verapdf's PDF/UA-2 profile.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
- fully incorporated back sayamindu's stuff for dealing with encrypted
signatures files (not a bad idea!)
- removed an old uw-header file from a previous version
