docs(ios): track ReplayKit screen-broadcast + native audio-routing as phase-2 follow-ups

iOS WebViews don't support getDisplayMedia, so sharing the device screen into a meeting needs a
native ReplayKit Broadcast Upload Extension (+ App Groups) — viewing a shared screen works today.
Also note native audio routing (AVAudioSession) as a phase-2 plugin. Adjusted the App Review note
so we don't advertise iOS screen-sharing before that extension ships.

mobile/IOS_SETUP.md

@@ -65,5 +65,27 @@ collect account info + usage for chat/calls). Then submit for review (or flip `s
 ### App Review note (Guideline 4.2 — "Minimum Functionality")
 Apple scrutinises apps that look like "just a website". Ours passes because it ships **real native
 capabilities** — push notifications, camera/microphone for calls, photo sharing. Make sure push (Step 5)
-is live before the **public** submission, and in the reviewer notes mention the native video calling +
+is live before the **public** submission, and in the reviewer notes mention the **native video/voice
-screen sharing so it's obvious this is more than a web view. TestFlight builds are fine without push.
+calling + push notifications**. Do **not** advertise "share your screen" as an iOS feature in the store
+listing yet — see the follow-up below (you can still *view* a screen someone else shares).
+
+---
+
+## Known iOS limitations & follow-ups (phase 2 — after TestFlight)
+
+### 1. Sharing YOUR iOS screen into a meeting → needs a ReplayKit Broadcast Upload Extension
+- **Why:** the app's screen share uses the web `getDisplayMedia` API, which **iOS WebViews and Safari do
+  not support**. Apple only allows capturing the *device* screen via **ReplayKit**.
+- **What works today on iOS:** *viewing* a screen another participant shares (it's just incoming video),
+  chat, voice/video calls, camera, photo sharing.
+- **What's needed to broadcast the iOS screen:** a native **Broadcast Upload Extension** target that
+  captures frames via ReplayKit and feeds them into the LiveKit/WebRTC session, plus the **App Groups**
+  capability (to pass data between the app and the extension). This is native Swift work — NOT part of
+  the Capacitor wrapper — so it's tracked as a separate task, done after the app is on TestFlight.
+- **Store impact:** don't claim iOS screen-sharing in the listing until this ships, or a reviewer may
+  test it and it will fail.
+
+### 2. Native mobile audio routing (speaker / earpiece / Bluetooth) — needs a Capacitor audio plugin
+- Mobile **web** can't switch the audio output route (`setSinkId` is unimplemented on iOS/Android), so the
+  in-meeting speaker/earpiece/Bluetooth control is web-only where it works and hidden where it doesn't.
+- True routing on iOS needs a small native plugin driving `AVAudioSession`. Phase-2 native task.