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/react-i18next/src/useSSR.js

@@ -0,0 +1,33 @@
+import { useContext } from 'react';
+import { getI18n, I18nContext } from './context.js';
+
+export const useSSR = (initialI18nStore, initialLanguage, props = {}) => {
+  const { i18n: i18nFromProps } = props;
+  const { i18n: i18nFromContext } = useContext(I18nContext) || {};
+  const i18n = i18nFromProps || i18nFromContext || getI18n();
+
+  // opt out if is a cloned instance, eg. created by i18next-http-middleware on request
+  // -> do not set initial stuff on server side
+  if (i18n.options && i18n.options.isClone) return;
+
+  // nextjs / SSR: getting data from next.js or other ssr stack
+  if (initialI18nStore && !i18n.initializedStoreOnce) {
+    i18n.services.resourceStore.data = initialI18nStore;
+
+    // add namespaces to the config - so a languageChange call loads all namespaces needed
+    i18n.options.ns = Object.values(initialI18nStore).reduce((mem, lngResources) => {
+      Object.keys(lngResources).forEach((ns) => {
+        if (mem.indexOf(ns) < 0) mem.push(ns);
+      });
+      return mem;
+    }, i18n.options.ns);
+
+    i18n.initializedStoreOnce = true;
+    i18n.isInitialized = true;
+  }
+
+  if (initialLanguage && !i18n.initializedLanguageOnce) {
+    i18n.changeLanguage(initialLanguage);
+    i18n.initializedLanguageOnce = true;
+  }
+};