WebKitGTK ships enable-media-stream/enable-webrtc off by default
(unlike WebView2/WKWebView), leaving navigator.mediaDevices undefined
and Element Call reporting "browser does not support WebRTC" on every
Linux build. Enable both settings and auto-grant the resulting
camera/mic permission request, mirroring the existing WebView2 handling.
Also add a build-arch CI job that repackages the existing .deb into a
real .pkg.tar.zst and uploads it to the Gitea release alongside the
Windows/Linux artifacts, for Arch/CachyOS users who'd rather use pacman
than an AppImage.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
