docs(wiki): v2.18.1 — document Label Sync event-driven triggers
docs: add Auto-Tagger and Label Sync wiki pages Documents the two automation features that shipped post-v2.17.0: Auto-Tagger (criteria-based Sonarr/Radarr tagging with composite rules, Connect webhooks, and TMDb/Trakt list-membership) and Label Sync (any-to-any tag/label propagation across Sonarr, Radarr, Plex, Jellyfin, Emby). Home.md sidebar gets entries for both pages under Automation, and the Overview table gains rows for both features. The new pages mirror the Library-Cleanup.md structure (Overview / Getting Started / How It Works / Configuration / Operations / Best Practices / Troubleshooting / API Reference) for navigation parity. Auto-Tagger.md links back to Library-Cleanup.md for the shared rule-types reference rather than duplicating it; only the two new list-membership rule types (tmdb_list_member, trakt_list_member) are documented in detail there.