Bumps base version 2.8.0 → 2.8.1 and the docker-publish default tag. Headline is the
Spotify/Deezer playlist export (#945); also the Library Reorganize rename-only mode (#875),
broader lossless handling (#941/#939), download + search fixes, the refined reduce-visual-effects
pass, and merged contributor PRs (#942/#943/#944).
Updates the five release touch-points: web_server version, docker-publish default, pr_description.md,
helper.js WHATS_NEW + VERSION_MODAL_SECTIONS (current release + Earlier-in-2.8.0 summary), and the
new RELEASE_2.8.1_discord.md.