fix: mobile dashboard navigation for Add Vehicle and Maintenance

- Add Vehicle now navigates to Vehicles screen and opens add form
- Add Maintenance mobile screen with records/schedules tabs
- Add 'Maintenance' to MobileScreen type
- Wire up onViewMaintenance callback to navigate to Maintenance screen

refs #2

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

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

frontend/src/App.tsx

@@ -27,6 +27,7 @@ const StationsMobileScreen = lazy(() => import('./features/stations/mobile/Stati
 const VehiclesMobileScreen = lazy(() => import('./features/vehicles/mobile/VehiclesMobileScreen').then(m => ({ default: m.VehiclesMobileScreen })));
 const VehicleDetailMobile = lazy(() => import('./features/vehicles/mobile/VehicleDetailMobile').then(m => ({ default: m.VehicleDetailMobile })));
 const DocumentsMobileScreen = lazy(() => import('./features/documents/mobile/DocumentsMobileScreen'));
+const MaintenanceMobileScreen = lazy(() => import('./features/maintenance/mobile/MaintenanceMobileScreen'));
 
 // Admin pages (lazy-loaded)
 const AdminUsersPage = lazy(() => import('./pages/admin/AdminUsersPage').then(m => ({ default: m.AdminUsersPage })));
@@ -633,7 +634,12 @@ function App() {
                   <DashboardFeature
                     onNavigate={navigateToScreen}
                     onVehicleClick={handleVehicleSelect}
-                    onAddVehicle={() => setShowAddVehicle(true)}
+                    onViewMaintenance={() => navigateToScreen('Maintenance', { source: 'dashboard-maintenance' })}
+                    onAddVehicle={() => {
+                      setShowAddVehicle(true);
+                      navigateToScreen('Vehicles', { source: 'dashboard-add-vehicle' });
+                      navigateToVehicleSubScreen('add', undefined, { source: 'dashboard-add-vehicle' });
+                    }}
                   />
                 </MobileErrorBoundary>
               </motion.div>
@@ -685,6 +691,31 @@ function App() {
                 </MobileErrorBoundary>
               </motion.div>
             )}
+            {activeScreen === "Maintenance" && (
+              <motion.div
+                key="maintenance"
+                initial={{opacity:0, y:8}}
+                animate={{opacity:1, y:0}}
+                exit={{opacity:0, y:-8}}
+                transition={{ duration: 0.2, ease: "easeOut" }}
+              >
+                <MobileErrorBoundary screenName="Maintenance">
+                  <React.Suspense fallback={
+                    <div className="space-y-4">
+                      <GlassCard>
+                        <div className="p-4">
+                          <div className="text-slate-500 py-6 text-center">
+                            Loading maintenance screen...
+                          </div>
+                        </div>
+                      </GlassCard>
+                    </div>
+                  }>
+                    <MaintenanceMobileScreen />
+                  </React.Suspense>
+                </MobileErrorBoundary>
+              </motion.div>
+            )}
             {activeScreen === "Settings" && (
               <motion.div
                 key="settings"