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/postcss/lib/stringifier.d.ts

@@ -0,0 +1,46 @@
+import {
+  AnyNode,
+  AtRule,
+  Builder,
+  Comment,
+  Container,
+  Declaration,
+  Document,
+  Root,
+  Rule
+} from './postcss.js'
+
+declare namespace Stringifier {
+  // eslint-disable-next-line @typescript-eslint/no-use-before-define
+  export { Stringifier_ as default }
+}
+
+declare class Stringifier_ {
+  builder: Builder
+  constructor(builder: Builder)
+  atrule(node: AtRule, semicolon?: boolean): void
+  beforeAfter(node: AnyNode, detect: 'after' | 'before'): string
+  block(node: AnyNode, start: string): void
+  body(node: Container): void
+  comment(node: Comment): void
+  decl(node: Declaration, semicolon?: boolean): void
+  document(node: Document): void
+  raw(node: AnyNode, own: null | string, detect?: string): string
+  rawBeforeClose(root: Root): string | undefined
+  rawBeforeComment(root: Root, node: Comment): string | undefined
+  rawBeforeDecl(root: Root, node: Declaration): string | undefined
+  rawBeforeOpen(root: Root): string | undefined
+  rawBeforeRule(root: Root): string | undefined
+  rawColon(root: Root): string | undefined
+  rawEmptyBody(root: Root): string | undefined
+  rawIndent(root: Root): string | undefined
+  rawSemicolon(root: Root): boolean | undefined
+  rawValue(node: AnyNode, prop: string): string
+  root(node: Root): void
+  rule(node: Rule): void
+  stringify(node: AnyNode, semicolon?: boolean): void
+}
+
+declare class Stringifier extends Stringifier_ {}
+
+export = Stringifier