feat(songs): unified SongRow + paginated song results in search pages (#303)

Extracts the song-list row into a single shared <SongRow> component
used by Tracks Hub Browse, /search and /search/advanced. All three now
share the same five-column layout (Play+Enqueue · Title · Artist ·
Album · Genre · Duration), the same enqueueAndPlay click behaviour,
and the same right-click context menu / drag handler.

The header row is rendered separately via <SongListHeader> (kept
outside the virtualizer scroll container in the Tracks Hub so it
doesn't scroll away).

Both SearchResults and AdvancedSearch now infinite-scroll their song
results via an IntersectionObserver sentinel near the bottom of the
list (rootMargin 600 px). Pagination uses search3's songOffset; the
free-text branch in AdvancedSearch keeps applying genre/year filters
client-side per loaded page. Initial fetches stay at 50 (SearchResults)
and 100 (AdvancedSearch) songs; subsequent pages are 50 each.

Cleanup:
- removed the redundant `(N)` count in the AdvancedSearch songs heading
- dropped the unused `useNavigate` + `psyDrag` + per-page contextMenuSongId
  state in both search pages — SongRow handles those internally
- renamed the row-internal CSS classes from `.virtual-song-*` to
  `.song-list-row-*` so they read as shared, and switched the mobile
  grid breakpoint accordingly

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/SongRow.tsx

@@ -0,0 +1,116 @@
+import React, { memo } from 'react';
+import { useNavigate } from 'react-router-dom';
+import { Play, ListPlus } from 'lucide-react';
+import { useTranslation } from 'react-i18next';
+import type { SubsonicSong } from '../api/subsonic';
+import { usePlayerStore, songToTrack } from '../store/playerStore';
+import { enqueueAndPlay } from '../utils/playSong';
+import { useDragDrop } from '../contexts/DragDropContext';
+
+function fmtDuration(s: number): string {
+  if (!s || !isFinite(s)) return '–';
+  const m = Math.floor(s / 60);
+  const sec = Math.floor(s % 60);
+  return `${m}:${sec.toString().padStart(2, '0')}`;
+}
+
+interface Props {
+  song: SubsonicSong;
+}
+
+function SongRow({ song }: Props) {
+  const navigate = useNavigate();
+  const enqueue = usePlayerStore(s => s.enqueue);
+  const openContextMenu = usePlayerStore(s => s.openContextMenu);
+  const isCurrent = usePlayerStore(s => s.currentTrack?.id === song.id);
+  const psyDrag = useDragDrop();
+
+  return (
+    <div
+      className={`song-list-row${isCurrent ? ' is-current' : ''}`}
+      onDoubleClick={() => enqueueAndPlay(song)}
+      onContextMenu={(e) => {
+        e.preventDefault();
+        openContextMenu(e.clientX, e.clientY, song, 'song');
+      }}
+      onMouseDown={(e) => {
+        if (e.button !== 0) return;
+        const sx = e.clientX, sy = e.clientY;
+        const track = songToTrack(song);
+        const onMove = (me: MouseEvent) => {
+          if (Math.abs(me.clientX - sx) > 5 || Math.abs(me.clientY - sy) > 5) {
+            document.removeEventListener('mousemove', onMove);
+            document.removeEventListener('mouseup', onUp);
+            psyDrag.startDrag(
+              { data: JSON.stringify({ type: 'song', track }), label: song.title },
+              me.clientX, me.clientY,
+            );
+          }
+        };
+        const onUp = () => {
+          document.removeEventListener('mousemove', onMove);
+          document.removeEventListener('mouseup', onUp);
+        };
+        document.addEventListener('mousemove', onMove);
+        document.addEventListener('mouseup', onUp);
+      }}
+    >
+      <div className="song-list-row-cell song-list-row-actions">
+        <button
+          className="song-list-row-btn song-list-row-btn--play"
+          onClick={(e) => { e.stopPropagation(); enqueueAndPlay(song); }}
+          aria-label="Play"
+        >
+          <Play size={14} fill="currentColor" />
+        </button>
+        <button
+          className="song-list-row-btn"
+          onClick={(e) => { e.stopPropagation(); enqueue([songToTrack(song)]); }}
+          aria-label="Enqueue"
+        >
+          <ListPlus size={14} />
+        </button>
+      </div>
+      <div className="song-list-row-cell song-list-row-title truncate" title={song.title}>{song.title}</div>
+      <div className="song-list-row-cell truncate">
+        <span
+          className={song.artistId ? 'track-artist-link' : ''}
+          style={{ cursor: song.artistId ? 'pointer' : 'default' }}
+          onClick={(e) => { if (song.artistId) { e.stopPropagation(); navigate(`/artist/${song.artistId}`); } }}
+          title={song.artist}
+        >{song.artist}</span>
+      </div>
+      <div className="song-list-row-cell truncate">
+        {song.albumId ? (
+          <span
+            className="track-artist-link"
+            style={{ cursor: 'pointer' }}
+            onClick={(e) => { e.stopPropagation(); navigate(`/album/${song.albumId}`); }}
+            title={song.album}
+          >{song.album}</span>
+        ) : <span title={song.album}>{song.album}</span>}
+      </div>
+      <div className="song-list-row-cell song-list-row-genre truncate" title={song.genre ?? ''}>
+        {song.genre ?? '—'}
+      </div>
+      <div className="song-list-row-cell song-list-row-duration">{fmtDuration(song.duration)}</div>
+    </div>
+  );
+}
+
+/** Column header with the same grid as <SongRow>. Optional — pages can render it above the list. */
+export function SongListHeader() {
+  const { t } = useTranslation();
+  return (
+    <div className="song-list-row song-list-row--header" role="row">
+      <div className="song-list-row-cell song-list-row-actions" />
+      <div className="song-list-row-cell">{t('albumDetail.trackTitle')}</div>
+      <div className="song-list-row-cell">{t('albumDetail.trackArtist')}</div>
+      <div className="song-list-row-cell">{t('albumDetail.trackAlbum')}</div>
+      <div className="song-list-row-cell">{t('randomMix.trackGenre')}</div>
+      <div className="song-list-row-cell song-list-row-duration">{t('albumDetail.trackDuration')}</div>
+    </div>
+  );
+}
+
+export default memo(SongRow);