fix: add dashboard to navigation and set as default landing page (refs #2)

- Add Dashboard to desktop sidebar navigation (first item)
- Add /garage/dashboard route for desktop
- Change default redirect from /garage/vehicles to /garage/dashboard
- Change mobile default screen from Vehicles to Dashboard
- Create DashboardPage wrapper for desktop route

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/features/dashboard/index.ts

@@ -3,6 +3,7 @@
  */
 
 export { DashboardScreen } from './components/DashboardScreen';
+export { DashboardPage } from './pages/DashboardPage';
 export { SummaryCards, SummaryCardsSkeleton } from './components/SummaryCards';
 export { VehicleAttention, VehicleAttentionSkeleton } from './components/VehicleAttention';
 export { QuickActions, QuickActionsSkeleton } from './components/QuickActions';

frontend/src/features/dashboard/pages/DashboardPage.tsx

@@ -0,0 +1,53 @@
+/**
+ * @ai-summary Desktop dashboard page wrapping the DashboardScreen component
+ */
+
+import React from 'react';
+import { useNavigate } from 'react-router-dom';
+import { Box, Typography } from '@mui/material';
+import { DashboardScreen } from '../components/DashboardScreen';
+import { MobileScreen } from '../../../core/store';
+import { Vehicle } from '../../vehicles/types/vehicles.types';
+
+export const DashboardPage: React.FC = () => {
+  const navigate = useNavigate();
+
+  // Map mobile screen names to desktop routes
+  const handleNavigate = (screen: MobileScreen) => {
+    switch (screen) {
+      case 'Vehicles':
+        navigate('/garage/vehicles');
+        break;
+      case 'Log Fuel':
+        navigate('/garage/fuel-logs');
+        break;
+      case 'Stations':
+        navigate('/garage/stations');
+        break;
+      case 'Documents':
+        navigate('/garage/documents');
+        break;
+      case 'Settings':
+        navigate('/garage/settings');
+        break;
+      default:
+        navigate('/garage/dashboard');
+    }
+  };
+
+  const handleVehicleClick = (vehicle: Vehicle) => {
+    navigate(`/garage/vehicles/${vehicle.id}`);
+  };
+
+  return (
+    <Box sx={{ py: 2 }}>
+      <Typography variant="h4" sx={{ fontWeight: 700, color: 'text.primary', mb: 4 }}>
+        Dashboard
+      </Typography>
+      <DashboardScreen
+        onNavigate={handleNavigate}
+        onVehicleClick={handleVehicleClick}
+      />
+    </Box>
+  );
+};