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/merge-stream/README.md

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+# merge-stream
+
+Merge (interleave) a bunch of streams.
+
+[![build status](https://secure.travis-ci.org/grncdr/merge-stream.svg?branch=master)](http://travis-ci.org/grncdr/merge-stream)
+
+## Synopsis
+
+```javascript
+var stream1 = new Stream();
+var stream2 = new Stream();
+
+var merged = mergeStream(stream1, stream2);
+
+var stream3 = new Stream();
+merged.add(stream3);
+merged.isEmpty();
+//=> false
+```
+
+## Description
+
+This is adapted from [event-stream](https://github.com/dominictarr/event-stream) separated into a new module, using Streams3.
+
+## API
+
+### `mergeStream`
+
+Type: `function`
+
+Merges an arbitrary number of streams. Returns a merged stream.
+
+#### `merged.add`
+
+A method to dynamically add more sources to the stream. The argument supplied to `add` can be either a source or an array of sources.
+
+#### `merged.isEmpty`
+
+A method that tells you if the merged stream is empty.
+
+When a stream is "empty" (aka. no sources were added), it could not be returned to a gulp task.
+
+So, we could do something like this:
+
+```js
+stream = require('merge-stream')();
+// Something like a loop to add some streams to the merge stream
+// stream.add(streamA);
+// stream.add(streamB);
+return stream.isEmpty() ? null : stream;
+```
+
+## Gulp example
+
+An example use case for **merge-stream** is to combine parts of a task in a project's **gulpfile.js** like this:
+
+```js
+const gulp =          require('gulp');
+const htmlValidator = require('gulp-w3c-html-validator');
+const jsHint =        require('gulp-jshint');
+const mergeStream =   require('merge-stream');
+
+function lint() {
+  return mergeStream(
+    gulp.src('src/*.html')
+      .pipe(htmlValidator())
+      .pipe(htmlValidator.reporter()),
+    gulp.src('src/*.js')
+      .pipe(jsHint())
+      .pipe(jsHint.reporter())
+  );
+}
+gulp.task('lint', lint);
+```
+
+## License
+
+MIT