perf(14-03): add notification batching to queue store and granular change tracking to library store

- Queue store now uses queueMicrotask batching (matching library store pattern)
- Library store adds changeGeneration counter incremented only on actual data changes
- LibraryController checks changeGeneration before requestUpdate, skipping loading-only transitions
- Reduces unnecessary component re-renders during data loading cycles

frontend/src/store/queue-store.ts

@@ -52,6 +52,7 @@ class QueueStore {
   };
 
   private subscribers = new Set<Subscriber>();
+  private notifyScheduled = false;
 
   constructor() {
     this.initializeEventListeners();
@@ -268,7 +269,14 @@ class QueueStore {
   }
 
   private notify(): void {
-    this.subscribers.forEach((callback) => callback());
+    if (this.notifyScheduled) return;
+    this.notifyScheduled = true;
+    queueMicrotask(() => {
+      this.notifyScheduled = false;
+      for (const sub of this.subscribers) {
+        sub();
+      }
+    });
   }
 }