feat(bot): add QR PNG renderer

apps/bot/src/whatsapp/qr-renderer.test.ts

@@ -0,0 +1,15 @@
+import { describe, expect, it } from "vitest";
+import { renderQrPng } from "./qr-renderer.js";
+
+describe("renderQrPng", () => {
+  it("returns a PNG buffer for a non-empty string", async () => {
+    const png = await renderQrPng("test-qr-payload");
+    expect(png).toBeInstanceOf(Buffer);
+    expect(png[0]).toBe(0x89);
+    expect(png.subarray(1, 4).toString("ascii")).toBe("PNG");
+  });
+
+  it("rejects empty input", async () => {
+    await expect(renderQrPng("")).rejects.toThrow();
+  });
+});

apps/bot/src/whatsapp/qr-renderer.ts

@@ -0,0 +1,6 @@
+import QRCode from "qrcode";
+
+export async function renderQrPng(payload: string): Promise<Buffer> {
+  if (!payload) throw new Error("renderQrPng: payload is empty");
+  return await QRCode.toBuffer(payload, { type: "png", width: 512, margin: 2 });
+}