feat: Passwordless cross-device authentication

- Arkitektur: docs/auth/passwordless-architecture.md
- Backend: iom/quixzoom-auth-service/ (FastAPI + Redis)
- Webb: quixzoom-market-pages/se/login/ (QR-kod + polling)
- App: iom/quixzoom-app/src/features/auth/ (push + deep links)

Flöde: QR-kod → app-godkännande → webb-inloggad

landvex/node_modules/get-stream/buffer-stream.js

@@ -0,0 +1,52 @@
+'use strict';
+const {PassThrough: PassThroughStream} = require('stream');
+
+module.exports = options => {
+	options = {...options};
+
+	const {array} = options;
+	let {encoding} = options;
+	const isBuffer = encoding === 'buffer';
+	let objectMode = false;
+
+	if (array) {
+		objectMode = !(encoding || isBuffer);
+	} else {
+		encoding = encoding || 'utf8';
+	}
+
+	if (isBuffer) {
+		encoding = null;
+	}
+
+	const stream = new PassThroughStream({objectMode});
+
+	if (encoding) {
+		stream.setEncoding(encoding);
+	}
+
+	let length = 0;
+	const chunks = [];
+
+	stream.on('data', chunk => {
+		chunks.push(chunk);
+
+		if (objectMode) {
+			length = chunks.length;
+		} else {
+			length += chunk.length;
+		}
+	});
+
+	stream.getBufferedValue = () => {
+		if (array) {
+			return chunks;
+		}
+
+		return isBuffer ? Buffer.concat(chunks, length) : chunks.join('');
+	};
+
+	stream.getBufferedLength = () => length;
+
+	return stream;
+};