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/fs-extra/lib/output/index.js

@@ -0,0 +1,40 @@
+'use strict'
+
+const u = require('universalify').fromCallback
+const fs = require('graceful-fs')
+const path = require('path')
+const mkdir = require('../mkdirs')
+const pathExists = require('../path-exists').pathExists
+
+function outputFile (file, data, encoding, callback) {
+  if (typeof encoding === 'function') {
+    callback = encoding
+    encoding = 'utf8'
+  }
+
+  const dir = path.dirname(file)
+  pathExists(dir, (err, itDoes) => {
+    if (err) return callback(err)
+    if (itDoes) return fs.writeFile(file, data, encoding, callback)
+
+    mkdir.mkdirs(dir, err => {
+      if (err) return callback(err)
+
+      fs.writeFile(file, data, encoding, callback)
+    })
+  })
+}
+
+function outputFileSync (file, ...args) {
+  const dir = path.dirname(file)
+  if (fs.existsSync(dir)) {
+    return fs.writeFileSync(file, ...args)
+  }
+  mkdir.mkdirsSync(dir)
+  fs.writeFileSync(file, ...args)
+}
+
+module.exports = {
+  outputFile: u(outputFile),
+  outputFileSync
+}