chore: README update for new Molly UP mechanism

Author: pcrockett

README.md

@@ -3,6 +3,18 @@
 Get Signal push notifications without Google Play Services, and without killing your phone's
 battery. A secure, free, low-maintenance solution using [Fly.io](https://fly.io).
 
+---
+
+**IMPORTANT UPDATE 2024-12-04:** Good news! Unified push has been merged into the main Molly
+app, and the old "unified push" flavor of the app is now deprecated. There also seem to be some
+usability improvements around getting it set up. That said, I don't have time to look into them
+now, so these instructions are now old. In the next few days I'll get around to bringing them
+up-to-date.
+
+See [this issue](https://github.com/pcrockett/mollysocket-fly/issues/15) for more details.
+
+---
+
 **Table of Contents:**
 
 * [What we're building and why](doc/WHAT_WHY.md)