Messages are marked as read even though the message has not been read

Steps to reproduce

1. User A sends a message to User B
2. User B has Talk installed on Android, app is not open
3. Push notification arrives on User B's device
4. Message is immediately marked as read for User A, without User B opening the chat

Expected behaviour

Messages should not instantly be marked as read

Actual behaviour

Messages sent to an user with android are instantly marked as read, even though the User receiving the message is offline and the app is not open.

Device brand and model

Samsung s24

Android version

Unknown

Nextcloud Talk app version

23.0.1

Nextcloud server version

34.0.0.12

Talk version

No response

Custom Signaling server configured

Yes (specify version in Additional Information)

Custom TURN server configured

Yes

Custom STUN server configured

None

Android logs

No response

Server log

{"user":"audi","method":"GET","url":"/ocs/v2.php/apps/spreed/api/v1/chat/h92fgma6?lastKnownMessageId=57708&setReadMarker=1&timeout=30&lookIntoFuture=1","userAgent":"Mozilla/5.0 (Android) Nextcloud-Talk v23.0.1"}

Additional information

The Android app polls with setReadMarker=1 during background activity triggered by push notifications. The user appears offline simultaneously (no active HPB/WebSocket session), confirming the app is not in the foreground. Background polls should use setReadMarker=0.

High performance backend version: 2.1.1~docker

Start by tracing the Android background activity triggered by push notifications and the poll request shown in the issue, including its setReadMarker parameter. Verify that background polling does not mark messages read while the app is closed, and confirm that messages are still marked read when the user actually opens the chat.