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/stream-buffers/lib/writable_streambuffer.js

@@ -0,0 +1,97 @@
+var util = require("util"),
+	stream = require("stream"),
+	constants = require("./constants");
+
+// TODO: clear up specs on returning false from a write and emitting a drain event.
+// Does this mean if I return false from a write, I should ignore any write requests between that false return and the drain event?
+var WritableStreamBuffer = module.exports = function(opts) {
+	var that = this;
+
+	stream.Stream.call(this);
+
+	opts = opts || {};
+	var initialSize = opts.initialSize || constants.DEFAULT_INITIAL_SIZE;
+	var incrementAmount = opts.incrementAmount || constants.DEFAULT_INCREMENT_AMOUNT;
+
+	var buffer = new Buffer(initialSize);
+	var size = 0;
+
+	this.writable = true;
+	this.readable = false;
+
+	this.size = function() {
+		return size;
+	};
+
+	this.maxSize = function() {
+		return buffer.length;
+	};
+
+	this.getContents = function(length) {
+		if(!size) return false;
+
+		var data = new Buffer(Math.min(length || size, size));
+		buffer.copy(data, 0, 0, data.length);
+
+		if(data.length < size)
+			buffer.copy(buffer, 0, data.length);
+
+		size -= data.length;
+
+		return data;
+	};
+
+	this.getContentsAsString = function(encoding, length) {
+		if(!size) return false;
+
+		var data = buffer.toString(encoding || "utf8", 0, Math.min(length || size, size));
+		var dataLength = Buffer.byteLength(data);
+
+		if(dataLength < size)
+			buffer.copy(buffer, 0, dataLength);
+
+		size -= dataLength;
+		return data;
+	};
+
+	var increaseBufferIfNecessary = function(incomingDataSize) {
+		if((buffer.length - size) < incomingDataSize) {
+			var factor = Math.ceil((incomingDataSize - (buffer.length - size)) / incrementAmount);
+
+			var newBuffer = new Buffer(buffer.length + (incrementAmount * factor));
+			buffer.copy(newBuffer, 0, 0, size);
+			buffer = newBuffer;
+		}
+	};
+
+	this.write = function(data, encoding, callback) {
+		if(!that.writable) return;
+
+		if(Buffer.isBuffer(data)) {
+			increaseBufferIfNecessary(data.length);
+			data.copy(buffer, size, 0);
+			size += data.length;
+		}
+		else {
+			data = data + "";
+			increaseBufferIfNecessary(Buffer.byteLength(data));
+			buffer.write(data, size, encoding || "utf8");
+			size += Buffer.byteLength(data);
+		}
+		
+		if(typeof callback === "function") { callback() ;}
+	};
+
+	this.end = function() {
+		var args = Array.prototype.slice.apply(arguments);
+		if(args.length) that.write.apply(that, args);
+		that.emit('finish');
+		that.destroy();
+	};
+
+	this.destroySoon = this.destroy = function() {
+		that.writable = false;
+		that.emit("close");
+	};
+};
+util.inherits(WritableStreamBuffer, stream.Stream);