perf(08-02): migrate track-list and queue-panel virtualizers to repeat() directive

- track-list uses repeat() with FilePath key for efficient DOM reuse
- queue-panel uses repeat() with QueueTrack.id key
- Removed .renderItem property, kept .items for virtualization sizing

frontend/src/components/queue-panel/queue-panel.ts

@@ -15,6 +15,7 @@ import type { PlaylistPicker } from '@components/playlist-picker/playlist-picker
 import '@lit-labs/virtualizer';
 import type { LitVirtualizer } from '@lit-labs/virtualizer';
 import { flow } from '@lit-labs/virtualizer/layouts/flow.js';
+import { repeat } from 'lit/directives/repeat.js';
 import type { QueueTrack } from '@store/queue-store';
 import { SelectionController } from '@utils/selection-controller';
 import type { SelectionHost } from '@utils/selection-controller';
@@ -1282,10 +1283,12 @@ export class QueuePanel
                               <lit-virtualizer
                                   scroller
                                   .items=${tracks}
-                                  .renderItem=${this
-                                      .renderTrackItem}
                                   .layout=${this.flowLayout}
-                              ></lit-virtualizer>
+                              >${repeat(
+                                  tracks,
+                                  (track) => track.id,
+                                  (track, index) => this.renderTrackItem(track, index),
+                              )}</lit-virtualizer>
                           `}
                 </div>
             </div>

frontend/src/components/track-list/track-list.ts

@@ -25,6 +25,7 @@ import {
     DEFAULT_COLUMN_IDS,
 } from './columns';
 import type { ColumnDef } from './columns';
+import { repeat } from 'lit/directives/repeat.js';
 import {
     rankTracks,
     highlightText,
@@ -1736,9 +1737,12 @@ export class TrackList extends LitElement implements SelectionHost, ContextMenuH
                       <lit-virtualizer
                         scroller
                         .items=${visibleTracks}
-                        .renderItem=${this.renderTrackRow}
                         .layout=${this.flowLayout}
-                      ></lit-virtualizer>
+                      >${repeat(
+                          visibleTracks,
+                          (track) => track.FilePath,
+                          (track, index) => this.renderTrackRow(track, index),
+                      )}</lit-virtualizer>
                     `}
 
       ${this.searchCtrl.term && visibleTracks.length > 0