feat(crdt): Create AwarenessManager for multi-user awareness

frontend/src/crdt/AwarenessManager.ts

@@ -0,0 +1,40 @@
+import { Awareness } from 'y-protocols/awareness';
+import * as Y from 'yjs';
+
+export class AwarenessManager {
+  awareness: Awareness;
+  
+  constructor(doc: Y.Doc) {
+    this.awareness = new Awareness(doc);
+  }
+
+  setLocalState(state: Record<string, any>) {
+    this.awareness.setLocalState(state);
+  }
+
+  getStates(): Map<number, Record<string, any>> {
+    return this.awareness.getStates();
+  }
+
+  on(event: 'change', callback: (updates: AwarenessUpdate) => void): void;
+  on(event: 'update', callback: (updates: AwarenessUpdate) => void): void;
+  on(event: string, callback: (updates: AwarenessUpdate) => void): void {
+    this.awareness.on(event as any, callback);
+  }
+
+  off(event: 'change', callback: (updates: AwarenessUpdate) => void): void;
+  off(event: 'update', callback: (updates: AwarenessUpdate) => void): void;
+  off(event: string, callback: (updates: AwarenessUpdate) => void): void {
+    this.awareness.off(event as any, callback);
+  }
+
+  destroy() {
+    this.awareness.destroy();
+  }
+}
+
+type AwarenessUpdate = {
+  added: number[];
+  updated: number[];
+  removed: number[];
+};