feat(05-01): dashboard grid, clock widget, widget registry, store, and tests

- Install react-grid-layout@2.2.3 and react-resizable
- Create widget-registry.tsx with all 4 widget types, WIDGET_CONSTRAINTS, WidgetProps
- Create dashboard-api.ts with fetch/save layout and widget CRUD functions
- Create dashboard-store.ts (Zustand, NO persist — D-05) with edit mode and auto-save on exit
- Create DashboardGrid with react-grid-layout v2 Responsive, ResizeObserver width
- Create ClockWidget using Intl.DateTimeFormat (no manual UTC offsets)
- Create WidgetWrapper with drag handle and delete button in edit mode
- Create EditModeToggle (pencil/checkmark), WidgetCatalogModal (2x2 grid)
- Rewrite portal page.tsx as dashboard with grid, edit toggle, widget catalog
- Add ResizeObserver polyfill in test setup, CSS mock support in vitest config
- All 5 tests green (dashboard grid + clock widget)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/web/vitest.config.ts

@@ -13,5 +13,11 @@ export default defineConfig({
     environment: 'jsdom',
     globals: true,
     setupFiles: ['./src/test/setup.ts'],
+    css: false,
+    server: {
+      deps: {
+        inline: ['react-grid-layout', 'react-resizable'],
+      },
+    },
   },
 });