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/yaml/dist/stringify/stringifyNumber.js

@@ -0,0 +1,27 @@
+'use strict';
+
+function stringifyNumber({ format, minFractionDigits, tag, value }) {
+    if (typeof value === 'bigint')
+        return String(value);
+    const num = typeof value === 'number' ? value : Number(value);
+    if (!isFinite(num))
+        return isNaN(num) ? '.nan' : num < 0 ? '-.inf' : '.inf';
+    let n = Object.is(value, -0) ? '-0' : JSON.stringify(value);
+    if (!format &&
+        minFractionDigits &&
+        (!tag || tag === 'tag:yaml.org,2002:float') &&
+        /^-?\d/.test(n) &&
+        !n.includes('e')) {
+        let i = n.indexOf('.');
+        if (i < 0) {
+            i = n.length;
+            n += '.';
+        }
+        let d = minFractionDigits - (n.length - i - 1);
+        while (d-- > 0)
+            n += '0';
+    }
+    return n;
+}
+
+exports.stringifyNumber = stringifyNumber;