feat: v1.30.0 — Discord RPC, offline bulk download, artist images, lazy loading, crossfade fix

- Discord Rich Presence (opt-in) — requested by @Bewenben (#49)
- Bulk offline download for playlists and artist discographies — requested by @Apollosport (#54)
- Offline Library filter tabs: All / Albums / Playlists / Discographies with artist grouping
- Artist images on Artists overview (opt-in, off by default) — reported by @Apollosport (#53)
- Image lazy loading via IntersectionObserver (300px margin) across all pages
- Fix: crossfade no longer triggers on manual track skip — reported by @netherguy4 (#35)
- Fix: playlist offline cache now stored as single entry (not per-album)
- Fix: image cache AbortController no longer blocks IDB writes
- Update toast: experimental auto-update hint + GH download link always visible (Win/Mac)
- Queue tech strip: genre removed
- Facebook theme: contrast, opaque badge/back button, queue tab labels
- "Save discography offline" label (was "Download discography")
- Fix: clearing empty playlists via updatePlaylist.view (Axios empty array workaround)
- starredOverrides propagated to AlbumDetail, Favorites, RandomMix

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src-tauri/src/lib.rs

@@ -2,6 +2,7 @@
 #![cfg_attr(not(debug_assertions), windows_subsystem = "windows")]
 
 mod audio;
+mod discord;
 
 use std::collections::HashMap;
 use std::sync::Mutex;
@@ -340,6 +341,7 @@ pub fn run() {
     tauri::Builder::default()
         .manage(audio_engine)
         .manage(ShortcutMap::default())
+        .manage(discord::DiscordState::new())
         .plugin(tauri_plugin_updater::Builder::new().build())
         .plugin(tauri_plugin_process::init())
         .plugin(tauri_plugin_window_state::Builder::default().build())
@@ -538,6 +540,8 @@ pub fn run() {
             audio::audio_set_crossfade,
             audio::audio_set_gapless,
             audio::audio_chain_preload,
+            discord::discord_update_presence,
+            discord::discord_clear_presence,
             lastfm_request,
             download_track_offline,
             delete_offline_track,