LB Sync tab: fix track counts + auto-mirror on discovery complete

Two follow-ups to the LB Sync tab work:

1. **Track counts all showed 0.** The
   ``/api/discover/listenbrainz/*`` endpoints assemble a JSPF-shaped
   payload but drop the cached ``track_count`` field from the
   underlying ``listenbrainz_playlists`` row — the JSON the frontend
   sees only carries ``title`` / ``creator`` / ``annotation`` / an
   empty ``track`` array. The Discover-page renderer worked around
   it by hard-coding a fallback of 50; the Sync-page renderer had
   no such fallback, so every card displayed "0 tracks". Backend
   now includes ``track_count`` directly in each playlist payload
   (it's already in the cached row) so any frontend can render an
   accurate count without resorting to a default. JS still falls
   back to ``annotation.track_count`` and then ``track.length`` for
   older callers.

2. **LB playlists never landed in Mirrored Playlists.** The
   existing ``/api/listenbrainz/sync/start/<mbid>`` endpoint runs
   the converted Spotify tracks through ``_run_sync_task`` — i.e.
   it pushes them to the user's media server (Plex / Jellyfin /
   Navidrome / SoulSync) as a server-side playlist. It does NOT
   call ``database.mirror_playlist``. So no ``mirrored_playlists``
   row gets created and the playlist can't be picked up by the
   Auto-Sync scheduler, can't show up under the Mirrored tab,
   doesn't participate in pipeline automations — the whole point
   of the Sync-tab unification.

   Tidal works because Tidal mirrors on tab load with raw tracks
   then enriches via discovery. LB tracks only have provider IDs
   *after* discovery, so the equivalent moment for LB is "discovery
   complete". Added ``_mirrorListenBrainzAfterDiscovery(mbid)``
   that pulls the matched ``spotify_data`` out of
   ``discovery_results`` and posts to ``/api/mirror-playlist`` via
   the existing ``mirrorPlaylist`` helper. Hooked into both the
   WebSocket and HTTP-poll completion handlers of
   ``startListenBrainzDiscoveryPolling``. UPSERT-keyed on (source,
   source_playlist_id, profile_id), so re-running discovery is a
   safe no-op refresh.

Result: any LB playlist the user discovers (from either the
Discover page or the new Sync tab) now lands in
``mirrored_playlists`` with ``source='listenbrainz'`` + matched
tracks carrying canonical ``extra_data`` JSON, ready for the
Auto-Sync refresh + sync pipeline wired up in Phase 1a + 1b.

web_server.py

@@ -29986,6 +29986,7 @@ def _get_lb_discover_playlists(playlist_type):
                 "identifier": f"https://listenbrainz.org/playlist/{playlist['playlist_mbid']}",
                 "title": playlist['title'],
                 "creator": playlist['creator'],
+                "track_count": playlist.get('track_count', 0),
                 "annotation": playlist.get('annotation', {}),
                 "track": []
             }

webui/static/sync-listenbrainz.js

@@ -96,7 +96,9 @@ function renderListenBrainzSyncPlaylists() {
         const title = inner.title || inner.name || 'ListenBrainz Playlist';
         const creator = inner.creator || 'ListenBrainz';
         let count = 0;
-        if (inner.annotation && inner.annotation.track_count) {
+        if (inner.track_count) {
+            count = inner.track_count;
+        } else if (inner.annotation && inner.annotation.track_count) {
             count = inner.annotation.track_count;
         } else if (Array.isArray(inner.track) && inner.track.length > 0) {
             count = inner.track.length;

webui/static/sync-services.js

@@ -10793,6 +10793,72 @@ async function resetBeatportChart(urlHash) {
 // LISTENBRAINZ PLAYLIST DISCOVERY & SYNC
 // ============================================================================
 
+/**
+ * Auto-mirror a ListenBrainz playlist into the mirrored_playlists
+ * table after discovery completes. Pattern parity with Tidal —
+ * Tidal mirrors on tab load with raw tracks, then discovery enriches;
+ * LB tracks only have provider IDs after discovery, so we mirror at
+ * the end. Idempotent (UPSERT on source + source_playlist_id +
+ * profile_id), so calling it twice is a no-op.
+ */
+function _mirrorListenBrainzAfterDiscovery(playlistMbid) {
+    try {
+        const state = listenbrainzPlaylistStates[playlistMbid];
+        if (!state || !state.playlist) return;
+        if (typeof mirrorPlaylist !== 'function') return;
+
+        const results = state.discovery_results || [];
+        if (!results.length) return;
+
+        const tracks = results
+            .filter(r => r && r.spotify_data && r.spotify_data.id)
+            .map(r => {
+                const sp = r.spotify_data;
+                const artistName = Array.isArray(sp.artists)
+                    ? (typeof sp.artists[0] === 'object' ? sp.artists[0].name : sp.artists[0])
+                    : (sp.artists || '');
+                const albumName = (sp.album && typeof sp.album === 'object')
+                    ? sp.album.name : (sp.album || '');
+                const albumImage = (sp.album && sp.album.images && sp.album.images[0])
+                    ? sp.album.images[0].url : (sp.image_url || null);
+                return {
+                    track_name: sp.name || '',
+                    artist_name: artistName || '',
+                    album_name: albumName || '',
+                    duration_ms: sp.duration_ms || 0,
+                    image_url: albumImage,
+                    source_track_id: sp.id || '',
+                    extra_data: JSON.stringify({
+                        discovered: true,
+                        provider: sp.source || 'spotify',
+                        confidence: r.confidence || 1.0,
+                        matched_data: sp,
+                    }),
+                };
+            });
+
+        if (!tracks.length) {
+            console.warn(`🪞 [LB Mirror] No matched tracks in '${state.playlist.name}', skipping mirror`);
+            return;
+        }
+
+        mirrorPlaylist(
+            'listenbrainz',
+            playlistMbid,
+            state.playlist.name || 'ListenBrainz Playlist',
+            tracks,
+            {
+                owner: state.playlist.creator || 'ListenBrainz',
+                description: state.playlist.description || '',
+                image_url: state.playlist.image_url || '',
+            }
+        );
+        console.log(`🪞 [LB Mirror] Mirrored '${state.playlist.name}' with ${tracks.length} matched tracks`);
+    } catch (err) {
+        console.warn('LB mirror-after-discovery failed:', err);
+    }
+}
+
 function startListenBrainzDiscoveryPolling(playlistMbid) {
     console.log(`🔄 Starting ListenBrainz discovery polling for: ${playlistMbid}`);
 
@@ -10843,6 +10909,10 @@ function startListenBrainzDiscoveryPolling(playlistMbid) {
                 const playlistIdEl = `discover-lb-playlist-${playlistMbid}`;
                 const syncBtn = document.getElementById(`${playlistIdEl}-sync-btn`);
                 if (syncBtn) syncBtn.style.display = 'inline-block';
+                // Mirror matched tracks → mirrored_playlists table so the
+                // playlist participates in Auto-Sync schedules just like
+                // Tidal / Qobuz / Spotify mirrors do.
+                _mirrorListenBrainzAfterDiscovery(playlistMbid);
                 showToast('ListenBrainz discovery complete!', 'success');
             }
         };
@@ -10935,6 +11005,9 @@ function startListenBrainzDiscoveryPolling(playlistMbid) {
                 }
 
                 console.log('✅ ListenBrainz discovery complete:', playlistMbid);
+                // Mirror matched tracks → mirrored_playlists table so
+                // the playlist participates in Auto-Sync schedules.
+                _mirrorListenBrainzAfterDiscovery(playlistMbid);
                 showToast('ListenBrainz discovery complete!', 'success');
             }