feat(crdt): Create YjsDocument class with project structure

frontend/src/crdt/YjsDocument.ts

@@ -0,0 +1,62 @@
+import * as Y from 'yjs';
+
+type ProjectMeta = {
+  id: string;
+  name: string;
+  createdAt: number;
+  updatedAt: number;
+};
+
+type Layer = {
+  id: string;
+  name: string;
+  visible: boolean;
+  locked: boolean;
+};
+
+type Element = {
+  id: string;
+  type: string;
+  layerId: string;
+  x: number;
+  y: number;
+  width: number;
+  height: number;
+  properties: Record<string, any>;
+};
+
+type Block = {
+  id: string;
+  name: string;
+  elements: string[]; // element IDs
+};
+
+type BlockInstance = {
+  id: string;
+  blockId: string;
+  x: number;
+  y: number;
+  properties: Record<string, any>;
+};
+
+export class YjsDocument {
+  doc: Y.Doc;
+  projectMeta: Y.Map<any>;
+  layers: Y.Map<Layer>;
+  elements: Y.Array<Element>;
+  blocks: Y.Map<Block>;
+  blockInstances: Y.Array<BlockInstance>;
+
+  constructor() {
+    this.doc = new Y.Doc();
+    this.projectMeta = this.doc.getMap('projectMeta');
+    this.layers = this.doc.getMap('layers');
+    this.elements = this.doc.getArray('elements');
+    this.blocks = this.doc.getMap('blocks');
+    this.blockInstances = this.doc.getArray('blockInstances');
+  }
+
+  destroy() {
+    this.doc.destroy();
+  }
+}