fix(call): fix native crashes, muted icons and state broadcast in calls

[mahibi]

This commit contains the code from #6039 (thank you @tareko !) as it needed to be combined with more fixes during it's review.

PeerConnectionWrapper — native crash fixes:

• Call peerConnection.close() before dataChannel.dispose() so the WebRTC signaling thread stops dispatching callbacks before native objects are freed
• Call peerConnection.close() outside the synchronized lock; holding the lock deadlocks because close() blocks waiting for the signaling thread, which itself needs the lock to run its callbacks
• Null out peerConnection before calling close() so in-flight callbacks see null and return early instead of NPE-ing on peerConnection.hashCode() in onIceConnectionChange, onCreateFailure, and onSetFailure
• Call dataChannel.unregisterObserver() before dispose() in both removePeerConnection() and onDataChannel() to prevent the native observer from calling back into a disposed Java DataChannel object

LocalStateBroadcasterNoMcu — initial mute state not sent to peers:

• IceConnectionStateObserver.job was never started, so local audio/video/ speaking state was never sent to newly connected participants; only a manual mute+unmute triggered a broadcast
• handleCallParticipantAdded now accepts the live StateFlow and uses first { it.isConnected } to send initial state exactly once when ICE connects; base class gets a concrete StateFlow overload that defaults to the existing snapshot path so MCU behaviour is unchanged
• Fix ParticipantHandler initial isConnected = false (was true), which caused retrying when ICE actually connected

ParticipantHandler — guest audio not detected (cherry-pick of PR #6039):

• handleStreamChange() now sets isAudioEnabled from audio track presence, not only isStreamEnabled from video tracks; guests whose DataChannel never opens were permanently shown as muted despite having an active audio track
• handleIceConnectionStateChange() preserves audio/video state during ICE NEW/CHECKING if tracks are still present, rather than resetting to false unconditionally and relying on a DataChannel message to restore it
• Add GuestAudioDetectionTest and diagnostic logging

AI-assistant: Claude Code v2.1.142 (Claude Sonnet 4.6)

🏁 Checklist

• ⛑️ Tests (unit and/or integration) are included or not needed
• 🔖 Capability is checked or not needed
• 🔙 Backport requests are created or not needed: /backport to stable-xx.x
• 📅 Milestone is set
• 🌸 PR title is meaningful (if it should be in the changelog: is it meaningful to users?)

[github-actions]

APK file: https://github.com/nextcloud/talk-android/actions/runs/26644548422/artifacts/7293967270
To test this change/fix you can simply download above APK file and install and test it in parallel to your existing Nextcloud app.
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[mahibi]

/backport to stable-24.0

[github-actions]

APK file: https://github.com/nextcloud/talk-android/actions/runs/26645620132/artifacts/7294400520
To test this change/fix you can simply download above APK file and install and test it in parallel to your existing Nextcloud app.
(please click on link to get QR code displayed)