feat(smart-app): implement complete mobile app MVP

- App.tsx: full navigation (Auth stack + Main tabs with 5 screens)
- Auth: LoginScreen, RegisterScreen, ForgotPasswordScreen
- HomeScreen: dashboard with IoT metrics, weather widget, alerts, quick actions, sensors
- MapScreen: interactive map with layer toggles (6 layers)
- MarketplaceScreen: categories (6), products (5), search
- ChatScreen: AI chat with quick prompts (4), bot responses
- ProfileScreen: user info, stats, menu (9 items), logout
- AlertsScreen: alert list with severity, acknowledge
- SensorsScreen: sensor list with type filters (6 types), search
- ZonesScreen: zone cards with stats
- SettingsScreen: language picker (FR/EN/ES/DE), privacy, about
- Stores: iotStore (sensors, zones, alerts), notificationStore, uiStore + i18n
- Hooks: useSensors, useAlerts, useNotifications, useLocation
- Components: Card, Button, LoadingSpinner, ErrorBoundary, Header
- Services: iotService, notificationService (with axios API client)
- Utils: formatters (temp, AQI, noise, dates), validators (email, password, IBAN)
- Theme: colors.ts with full design system (Blue Ocean palette)
- Ditto: fixed MongoDB connection, new JWT secrets, official gateway image

smart-app-city/frontend/node_modules/use-latest-callback/src/index.ts

@@ -0,0 +1,34 @@
+import * as React from 'react';
+
+/**
+ * Use `useEffect` during SSR and `useLayoutEffect` in the Browser & React Native to avoid warnings.
+ */
+const useClientLayoutEffect =
+  typeof document !== 'undefined' ||
+  (typeof navigator !== 'undefined' && navigator.product === 'ReactNative')
+    ? React.useLayoutEffect
+    : React.useEffect;
+
+/**
+ * React hook which returns the latest callback without changing the reference.
+ */
+// eslint-disable-next-line @typescript-eslint/ban-types
+function useLatestCallback<T extends Function>(callback: T): T {
+  const ref = React.useRef<T>(callback);
+
+  const latestCallback = React.useRef(function latestCallback(
+    this: unknown,
+    ...args: unknown[]
+  ) {
+    return ref.current.apply(this, args);
+  } as unknown as T).current;
+
+  useClientLayoutEffect(() => {
+    ref.current = callback;
+  });
+
+  return latestCallback;
+}
+
+// Use export assignment to compile to module.exports =
+export = useLatestCallback;