v0.2.4-pre - call-return + UI fixes

Aurora 0.2.4-pre fixes call handling and tidies the UI, on top of 0.2.3-pre's peer-to-peer WebRTC transport.

Fixes

• Returning to the app during a call (via the app icon, the ongoing-call notification, or the floating bubble) now reliably brings the call screen back. Before, when the screen was recreated it could land on the home screen with no way back to the video, even though the call kept running.
• The connection status in the chat header is now a single tidy line; the full "couldn't connect directly" guidance shows as a banner above the conversation instead of crowding the header.
• Long contact names and the server-status line now truncate cleanly instead of wrapping.

Carried over from 0.2.3-pre

• Messages connect over a WebRTC data channel (ICE + self-hosted STUN, no relay), IPv6 first with IPv4 fallback and direct TCP on the same network. Both peers on symmetric carrier NAT with no IPv6 still cannot connect directly yet (a peer relay is future work).

Pre-alpha, experimental software. Do not trust it with anything critical yet. Sideload only (Android).