task(G2): layout bar UI + viewport minimap widget, zoomPan setView, canvas layout bridge

frontend/src/App.tsx

@@ -15,6 +15,7 @@ import CanvasArea from './components/CanvasArea';
 import RightSidebar from './components/RightSidebar';
 import CommandLine from './components/CommandLine';
 import StatusBar from './components/StatusBar';
+import LayoutBar from './components/LayoutBar';
 import MobileDrawers from './components/MobileDrawers';
 import BackgroundImport from './components/BackgroundImport';
 import HistoryPanel from './components/HistoryPanel';
@@ -1704,6 +1705,7 @@ const CADEditor: React.FC<CADEditorProps> = ({ projectId, token, onNavigateBack
         history={commandHistory}
         onCommand={handleCommand}
       />
+      <LayoutBar />
       <StatusBar
         snapEnabled={snapEnabled}
         orthoEnabled={orthoEnabled}