Rewrite sync module to work with SceneManager and v2 scene format
instead of Fabric.js. Key changes:
- setupSync takes SceneManager instead of Canvas
- broadcastScene uses sceneManager.serialize() for v2 SceneData
- broadcastTransform reads from item.data (x,y,sx,sy,angle)
- onSceneReceived uses diff-based loadScene (no flicker, no full reload)
- onTransformReceived updates item.data + displayObject directly
- Remove _suppress/resumeBroadcasts (diff-based loading is safe)
- Remove userInteracting/pendingScene deferral (not needed with diffs)
- Remove all Fabric.js imports and types
Hiren Kangad
9c5056d11e