feat(player): queue undo/redo with hotkeys and playback-aware restore

Snapshot queue, current track, time, and pause before queue mutations.
Ctrl+Z/Cmd+Z restores prior state; Ctrl+Shift+Z/Cmd+Shift+Z reapplies undone
edits when the redo stack is non-empty; new edits clear redo.

Resync the Rust audio engine only when the current song identity changes
from the pre-apply state so reorder/enqueue-style edits keep live playback.

Register the document capture listener from main.tsx after the window label
is set. Mini player forwards undo/redo via mini:undo-queue and mini:redo-queue.

src/components/MiniPlayer.tsx

@@ -221,6 +221,16 @@ export default function MiniPlayer() {
         return;
       }
 
+      if ((e.ctrlKey || e.metaKey) && (e.code === 'KeyZ' || e.key?.toLowerCase() === 'z')) {
+        e.preventDefault();
+        if (e.shiftKey) {
+          emit('mini:redo-queue', {}).catch(() => {});
+        } else {
+          emit('mini:undo-queue', {}).catch(() => {});
+        }
+        return;
+      }
+
       if (e.key === ' ' || e.code === 'Space') {
         e.preventDefault();
         emit('mini:control', 'toggle').catch(() => {});