feat(cloud): email unsubscribe (#258)

* feat(cloud): add email unsubscribe

* chore: add translations

packages/shared/src/utils/email.ts

@@ -0,0 +1,31 @@
+import { SignJWT } from "jose";
+
+const encoder = new TextEncoder();
+
+/**
+ * Creates a long‑lived unsubscribe link for a given user/subscriber.
+ *
+ * `${NEXT_PUBLIC_BASE_URL}/unsubscribe?token=<jwt>`
+ *
+ * The JWT payload only contains the subscriberId. There is no expiry
+ * on purpose – unsubscribe links should remain valid indefinitely.
+ *
+ */
+export async function createEmailUnsubscribeLink(
+  userId: string,
+): Promise<string | null> {
+  const baseUrl = process.env.NEXT_PUBLIC_BASE_URL;
+  const secret = process.env.EMAIL_UNSUBSCRIBE_SECRET;
+
+  if (!baseUrl || !secret) {
+    // Environment not configured for unsubscribe links.
+    return null;
+  }
+
+  const token = await new SignJWT({ subscriberId: userId })
+    .setProtectedHeader({ alg: "HS256" })
+    // No expiration on purpose; unsubscribe links are long‑lived.
+    .sign(encoder.encode(secret));
+
+  return `${baseUrl}/unsubscribe?token=${encodeURIComponent(token)}`;
+}