feat: enhance DashboardEditor and PageCanvasEditor with undo/redo, export/import, preview mode, i18n, keyboard shortcuts, mobile responsive layout

Co-authored-by: hotlong <50353452+hotlong@users.noreply.github.com>

Author: Copilot

packages/i18n/src/locales/en.ts

@@ -238,6 +238,21 @@ const en = {
     navImportSuccess: 'Navigation schema imported',
     navImportError: 'Invalid navigation JSON',
     navIconPlaceholder: 'Icon name (e.g. Users)',
+    dashboardEditor: 'Dashboard Editor',
+    noWidgets: 'No widgets. Click a button above to add one.',
+    widgetLayoutSize: 'Layout Size',
+    widgetWidth: 'Width',
+    widgetHeight: 'Height',
+    dashboardPreview: 'Dashboard Preview',
+    noWidgetsPreview: 'No widgets to preview',
+    pageCanvasEditor: 'Page Canvas Editor',
+    emptyPage: 'Empty page. Click a button above to add a component.',
+    pagePreview: 'Page Preview',
+    noComponentsPreview: 'No components to preview',
+    modePage: 'Page',
+    modeDashboard: 'Dashboard',
+    undo: 'Undo',
+    redo: 'Redo',
   },
   console: {
     title: 'ObjectStack Console',