Settings: choose a STUN server from Google, Cloudflare or a typed address

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -82,7 +82,7 @@ mumh5 keeps the foundation and replaces the experience.
 - Sound: on Linux one program or everything except mumh5 itself (through PipeWire, so viewers do not hear the voice chat twice); on Windows the whole system; in a browser what the browser offers
 - People in the channel see an indicator next to your name, on your tile and in your profile, and click to watch. The tiles above the chat fill a stage you can drag taller or shorter. A stream opens large, with everyone as a strip of tiles below, like a meeting, and can move to a window of its own; in the stacked layout it is just the picture, as wide as the chat. Sounds announce streams and viewers. Viewers set the stream's volume
 - No server setup and no extra account: the setup messages travel through the Mumble server, the stream goes directly between the two clients (WebRTC), up to 8 viewers. Regular Mumble clients do not see streams
-- Direct connections mean sharer and viewer see each other's IP address; mumh5 says so before the first use. Across the internet both sides need a STUN server. The browser version uses the one built into its proxy; in the desktop app you enter one in Settings, Voice (the proxy's address works there too), and none is contacted unless you do
+- Direct connections mean sharer and viewer see each other's IP address; mumh5 says so before the first use. Across the internet both sides need a STUN server. The browser version uses the one built into its proxy; in the desktop app you choose one in Settings, Voice (Google, Cloudflare, or any address such as your proxy's), and none is contacted unless you do
 - Tested between two desktop instances on one machine with a test picture. Sound capture, real screens, connections across the internet, Windows and the browser build are untested
 
 ### Chat