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/expo-file-system/ios/Encoding.swift

@@ -0,0 +1,88 @@
+// Copyright 2023-present 650 Industries. All rights reserved.
+
+import ExpoModulesCore
+
+enum Encoding: String, Enumerable {
+  // Equivalents of String.Encoding
+  case ascii
+  case nextstep
+  case japaneseeuc
+  case utf8
+  case isolatin1
+  case symbol
+  case nonlossyascii
+  case shiftjis
+  case isolatin2
+  case unicode
+  case windowscp1251
+  case windowscp1252
+  case windowscp1253
+  case windowscp1254
+  case windowscp1250
+  case iso2022jp
+  case macosroman
+  case utf16
+  case utf16bigendian
+  case utf16littleendian
+  case utf32
+  case utf32bigendian
+  case utf32littleendian
+
+  // Without equivalents in String.Encoding
+  case base64
+
+  func toStringEncoding() -> String.Encoding? {
+    switch self {
+    case .ascii:
+      return .ascii
+    case .nextstep:
+      return .nextstep
+    case .japaneseeuc:
+      return .japaneseEUC
+    case .utf8:
+      return .utf8
+    case .isolatin1:
+      return .isoLatin1
+    case .symbol:
+      return .symbol
+    case .nonlossyascii:
+      return .nonLossyASCII
+    case .shiftjis:
+      return .shiftJIS
+    case .isolatin2:
+      return .isoLatin2
+    case .unicode:
+      return .unicode
+    case .windowscp1251:
+      return .windowsCP1251
+    case .windowscp1252:
+      return .windowsCP1252
+    case .windowscp1253:
+      return .windowsCP1253
+    case .windowscp1254:
+      return .windowsCP1254
+    case .windowscp1250:
+      return .windowsCP1250
+    case .iso2022jp:
+      return .iso2022JP
+    case .macosroman:
+      return .macOSRoman
+    case .utf16:
+      return .utf16
+    case .utf16bigendian:
+      return .utf16BigEndian
+    case .utf16littleendian:
+      return .utf16LittleEndian
+    case .utf32:
+      return .utf32
+    case .utf32bigendian:
+      return .utf32BigEndian
+    case .utf32littleendian:
+      return .utf32LittleEndian
+
+      // Cases that don't have their own equivalent in String.Encoding
+    case .base64:
+      return nil
+    }
+  }
+}