docs: correct wiki against the 2026-10-01 code audit
docs: restructure wiki with user guide, developer pages and divided feature list Correct errors (ListenBrainz name, stale feature entries, migration count), update the feature list to 2.19.0 and divide it into seven topic pages, add a new Home page, sidebar and footer, add user guide pages (Installation, Podcasts, Internet Radio, Phone Sync, Troubleshooting) and developer pages (Architecture Overview, Building from Source, Testing).