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/@tanstack/react-query/src/QueryClientProvider.tsx

@@ -0,0 +1,45 @@
+'use client'
+import * as React from 'react'
+
+import type { QueryClient } from '@tanstack/query-core'
+
+export const QueryClientContext = React.createContext<QueryClient | undefined>(
+  undefined,
+)
+
+export const useQueryClient = (queryClient?: QueryClient) => {
+  const client = React.useContext(QueryClientContext)
+
+  if (queryClient) {
+    return queryClient
+  }
+
+  if (!client) {
+    throw new Error('No QueryClient set, use QueryClientProvider to set one')
+  }
+
+  return client
+}
+
+export type QueryClientProviderProps = {
+  client: QueryClient
+  children?: React.ReactNode
+}
+
+export const QueryClientProvider = ({
+  client,
+  children,
+}: QueryClientProviderProps): React.JSX.Element => {
+  React.useEffect(() => {
+    client.mount()
+    return () => {
+      client.unmount()
+    }
+  }, [client])
+
+  return (
+    <QueryClientContext.Provider value={client}>
+      {children}
+    </QueryClientContext.Provider>
+  )
+}