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/graphql/jsutils/Path.js.flow

@@ -0,0 +1,30 @@
+// @flow strict
+export type Path = {|
+  +prev: Path | void,
+  +key: string | number,
+  +typename: string | void,
+|};
+
+/**
+ * Given a Path and a key, return a new Path containing the new key.
+ */
+export function addPath(
+  prev: $ReadOnly<Path> | void,
+  key: string | number,
+  typename: string | void,
+): Path {
+  return { prev, key, typename };
+}
+
+/**
+ * Given a Path, return an Array of the path keys.
+ */
+export function pathToArray(path: ?$ReadOnly<Path>): Array<string | number> {
+  const flattened = [];
+  let curr = path;
+  while (curr) {
+    flattened.push(curr.key);
+    curr = curr.prev;
+  }
+  return flattened.reverse();
+}