fix: maintenance button navigates to maintenance screen (refs #2)

- Add onViewMaintenance prop to DashboardScreen
- Desktop: navigates to /garage/maintenance
- Mobile: falls back to Vehicles (no dedicated mobile maintenance screen)

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

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

frontend/src/features/dashboard/components/DashboardScreen.tsx

@@ -19,11 +19,13 @@ import { Vehicle } from '../../vehicles/types/vehicles.types';
 interface DashboardScreenProps {
   onNavigate?: (screen: MobileScreen, metadata?: Record<string, any>) => void;
   onVehicleClick?: (vehicle: Vehicle) => void;
+  onViewMaintenance?: () => void;
 }
 
 export const DashboardScreen: React.FC<DashboardScreenProps> = ({
   onNavigate,
-  onVehicleClick
+  onVehicleClick,
+  onViewMaintenance
 }) => {
   const { data: summary, isLoading: summaryLoading, error: summaryError } = useDashboardSummary();
   const { data: vehiclesNeedingAttention, isLoading: attentionLoading, error: attentionError } = useVehiclesNeedingAttention();
@@ -118,7 +120,7 @@ export const DashboardScreen: React.FC<DashboardScreenProps> = ({
       <QuickActions
         onAddVehicle={() => onNavigate?.('Vehicles')}
         onLogFuel={() => onNavigate?.('Log Fuel')}
-        onViewMaintenance={() => onNavigate?.('Vehicles')} // Navigate to vehicles then maintenance
+        onViewMaintenance={onViewMaintenance ?? (() => onNavigate?.('Vehicles'))}
         onViewVehicles={() => onNavigate?.('Vehicles')}
       />