feat(web): migrate dashboard to WidgetGrid with layout persistence (#497)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/web/src/components/widgets/__tests__/WidgetGrid.test.tsx

@@ -3,11 +3,20 @@
  * Following TDD - write tests first!
  */
 
-import { describe, it, expect, vi } from "vitest";
+import { describe, it, expect, vi, beforeAll } from "vitest";
 import { render, screen } from "@testing-library/react";
 import { WidgetGrid } from "../WidgetGrid";
 import type { WidgetPlacement } from "@mosaic/shared";
 
+// ResizeObserver is not available in jsdom
+beforeAll((): void => {
+  global.ResizeObserver = vi.fn().mockImplementation(() => ({
+    observe: vi.fn(),
+    unobserve: vi.fn(),
+    disconnect: vi.fn(),
+  }));
+});
+
 // Mock react-grid-layout
 vi.mock("react-grid-layout", () => ({
   default: ({ children }: { children: React.ReactNode }): React.JSX.Element => (