Docs: clarify ntfy privacy — default server is public ntfy.sh

The docs claimed ntfy keeps push metadata on your own infrastructure,
but the default NTFY_SERVER_URL is the public https://ntfy.sh cloud
service. Make explicit that push metadata (topic, notification title)
passes through ntfy.sh unless you self-host ntfy.

docs/playstore-listing.md

@@ -16,8 +16,9 @@ threads, media, search — Telegram-quality, on your own infrastructure.
 **Absolute Privacy!** — everything stays on your own infrastructure:
 
 - Your gateway, your machine, your data. No cloud middleman for chat.
-- **Push notifications:** ntfy by default — push metadata stays on your own
-  (self-hosted) ntfy server.
+- **Push notifications:** ntfy by default. Note: out of the box it uses the
+  public ntfy.sh service; self-host ntfy (one env var) to keep push metadata
+  on your own server.
 - **FCM is opt-in** (`IRIS_PUSH_BACKEND=fcm`): standard and reliable, but FCM
   push metadata (notification title, device token) is routed through
   **Google's servers**. If you want truly private communication, use ntfy
@@ -32,10 +33,12 @@ Runs on Android and desktop (Linux, macOS, Windows) from one shared codebase.
 ## Privacy note (for the "Data safety" section / FAQ)
 
 Iris talks directly to your own hermes gateway over a private, token-authenticated
-connection. By default, push notifications use ntfy, which you can self-host so
-that push metadata never leaves your infrastructure. If you explicitly enable
-FCM, push metadata (notification title, device token) is sent via Google's FCM
-servers; chat content itself is not sent to Google — FCM only carries a short
-preview, and full content is fetched from your gateway over the authenticated
+connection. By default, push notifications use ntfy — out of the box via the
+public ntfy.sh service (push metadata such as the topic and notification title
+passes through ntfy.sh's servers); self-host ntfy (one env var) so that push
+metadata never leaves your infrastructure. If you explicitly enable FCM, push
+metadata (notification title, device token) is sent via Google's FCM servers;
+chat content itself is not sent to Google — FCM only carries a short preview,
+and full content is fetched from your gateway over the authenticated
 connection. For truly private communication, use the default ntfy backend
-(self-hosted).
+with a self-hosted ntfy server.