Footer elements (notes, Worte/Weise metadata, reference book table) on
song pages now render at fixed positions anchored to the bottom margin
instead of flowing after song content. This ensures consistent vertical
positioning across all pages regardless of content length.
The footer area is computed from bottomMargin + footerReservation and
elements render top-down within it: notes -> metadata -> references.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
