feat(smart-app): complete all remaining components, screens, hooks, services, stores, i18n

- i18n/index.ts: i18next setup with FR/EN/ES/DE translations
- constants.ts: app config, sensor types, alert severity, storage keys, refresh intervals
- store/index.ts: barrel export for all stores
- iotStore.ts: full IoT store (6 sensors, 3 zones, 2 alerts) with actions
- notificationStore.ts: notification store (5 mock notifications) with actions
- uiStore.ts: theme/language store + translation maps for 4 languages
- useSensors.ts: sensor filtering by type/zone, alert sensors selector
- useAlerts.ts: active alerts, critical alerts, acknowledge
- useNotifications.ts: notification CRUD operations
- useLocation.ts: GPS location with expo-location, default Fort-de-France
- SensorCard.tsx: full sensor card with status dot, compact mode
- StatsCard.tsx: stats card with icon, value, trend
- AlertCard.tsx: alert card with severity bar, acknowledge button
- ZoneCard.tsx: zone card with color bar, sensor/alert counts
- LineChart.tsx: bar-based line chart with Y-axis labels
- BarChart.tsx: bar chart with value labels
- GaugeChart.tsx: semi-circular gauge with color thresholds
- MapView.tsx: map placeholder with overlay markers
- MarkerPopup.tsx: popup with title, value, status, detail button
- DashboardScreen.tsx: analytics dashboard with gauges + charts
- SensorDetailScreen.tsx: sensor detail with gauge + history chart
- NotificationPrefsScreen.tsx: notification preference toggles (4)
- LayerDetailScreen.tsx: layer detail placeholder
- iot.service.ts: CRUD operations for sensors, zones, alerts
- gis.service.ts: geocoding, POI search, routing

smart-app-city/frontend/src/utils/constants.ts

@@ -1 +1,53 @@
-// TODO: Implement
+// Smart App City — App Constants
+
+export const APP_NAME = 'Smart App City';
+export const APP_VERSION = '0.1.0';
+
+// API
+export const API_BASE_URL = process.env.EXPO_PUBLIC_API_URL ?? 'https://api-smartapp.digitribe.fr/api/v1';
+export const API_TIMEOUT = 15000;
+
+// Map
+export const DEFAULT_MAP_CENTER = { latitude: 14.6161, longitude: -61.0588 }; // Fort-de-France
+export const DEFAULT_MAP_ZOOM = 12;
+export const MARTINIQUE_BOUNDS = {
+  north: 14.88,
+  south: 14.45,
+  east: -60.82,
+  west: -61.23,
+};
+
+// Sensor types
+export const SENSOR_TYPES = [
+  { key: 'temperature', label: 'Température', unit: '°C', icon: '🌡️', color: '#00ACC1' },
+  { key: 'humidity', label: 'Humidité', unit: '%', icon: '💧', color: '#1565C0' },
+  { key: 'air_quality', label: 'Qualité Air', unit: 'AQI', icon: '🌬️', color: '#2E7D32' },
+  { key: 'noise', label: 'Bruit', unit: 'dB', icon: '🔊', color: '#3949AB' },
+  { key: 'traffic', label: 'Trafic', unit: 'veh/h', icon: '🚗', color: '#F57C00' },
+  { key: 'energy', label: 'Énergie', unit: 'kWh', icon: '⚡', color: '#D32F2F' },
+];
+
+// Alert severity
+export const ALERT_SEVERITY = {
+  critical: { label: 'Critique', color: '#D32F2F', icon: '🔴' },
+  high: { label: 'Haute', color: '#F57C00', icon: '🟠' },
+  medium: { label: 'Moyenne', color: '#FF9800', icon: '🟡' },
+  low: { label: 'Basse', color: '#0288D1', icon: '🔵' },
+};
+
+// Storage keys
+export const STORAGE_KEYS = {
+  ACCESS_TOKEN: 'access_token',
+  REFRESH_TOKEN: 'refresh_token',
+  AUTH_STORAGE: 'auth-storage',
+  THEME: 'theme',
+  LANGUAGE: 'language',
+};
+
+// Refresh intervals (ms)
+export const REFRESH_INTERVALS = {
+  SENSORS: 30000,    // 30s
+  ALERTS: 60000,     // 1min
+  WEATHER: 300000,   // 5min
+  NOTIFICATIONS: 30000, // 30s
+};