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-font/android/build.gradle

@@ -0,0 +1,19 @@
+apply plugin: 'com.android.library'
+
+group = 'host.exp.exponent'
+version = '12.0.10'
+
+def expoModulesCorePlugin = new File(project(":expo-modules-core").projectDir.absolutePath, "ExpoModulesCorePlugin.gradle")
+apply from: expoModulesCorePlugin
+applyKotlinExpoModulesCorePlugin()
+useCoreDependencies()
+useDefaultAndroidSdkVersions()
+useExpoPublishing()
+
+android {
+  namespace "expo.modules.font"
+  defaultConfig {
+    versionCode 29
+    versionName "12.0.10"
+  }
+}

smart-app-city/frontend/node_modules/expo-font/android/src/main/AndroidManifest.xml

@@ -0,0 +1,3 @@
+<manifest>
+
+</manifest>

smart-app-city/frontend/node_modules/expo-font/android/src/main/java/expo/modules/font/FontLoaderModule.kt

@@ -0,0 +1,74 @@
+// Copyright 2015-present 650 Industries. All rights reserved.
+
+package expo.modules.font
+
+import android.content.Context
+import android.graphics.Typeface
+import android.net.Uri
+import expo.modules.interfaces.font.FontManagerInterface
+import expo.modules.kotlin.exception.CodedException
+import expo.modules.kotlin.exception.Exceptions
+import expo.modules.kotlin.modules.Module
+import expo.modules.kotlin.modules.ModuleDefinition
+import java.io.File
+
+private const val ASSET_SCHEME = "asset://"
+
+private class FontManagerInterfaceNotFoundException :
+  CodedException("FontManagerInterface not found")
+
+private class FileNotFoundException(uri: String) :
+  CodedException("File '$uri' doesn't exist")
+
+open class FontLoaderModule : Module() {
+  private val context: Context
+    get() = appContext.reactContext ?: throw Exceptions.ReactContextLost()
+
+  @Suppress("MemberVisibilityCanBePrivate")
+  open val prefix = ""
+
+  override fun definition() = ModuleDefinition {
+    Name("ExpoFontLoader")
+
+    Constants("customNativeFonts" to queryCustomNativeFonts())
+
+    AsyncFunction("loadAsync") { fontFamilyName: String, localUri: String ->
+      val context = appContext.reactContext ?: throw Exceptions.ReactContextLost()
+
+      // TODO(nikki): make sure path is in experience's scope
+      val typeface: Typeface = if (localUri.startsWith(ASSET_SCHEME)) {
+        Typeface.createFromAsset(
+          context.assets, // Also remove the leading slash.
+          localUri.substring(ASSET_SCHEME.length + 1)
+        )
+      } else {
+        val file = Uri.parse(localUri).path?.let { File(it) }
+          ?: throw FileNotFoundException(localUri)
+
+        Typeface.createFromFile(file)
+      }
+
+      val fontManager = appContext.legacyModule<FontManagerInterface>()
+        ?: throw FontManagerInterfaceNotFoundException()
+
+      fontManager.setTypeface(prefix + fontFamilyName, Typeface.NORMAL, typeface)
+    }
+  }
+
+  /**
+   * Queries custom native font names from the assets.
+   * Alignment with React Native's implementation at:
+   * https://github.com/facebook/react-native/blob/363ee484b/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/common/assets/ReactFontManager.java#L146-L161
+   */
+  private fun queryCustomNativeFonts(): List<String> {
+    val assetManager = context.assets
+    val fontFileRegex = Regex("^(.+?)(_bold|_italic|_bold_italic)?\\.(ttf|otf)$")
+
+    return assetManager.list("fonts/")
+      ?.mapNotNull { fileName ->
+        fontFileRegex.find(fileName)?.groupValues?.get(1)
+      }
+      ?.filter { it.isNotBlank() }
+      .orEmpty()
+  }
+}