Move SFU authentication into livekit/auth and choose the endpoint by role

The OpenID flow moves to src/livekit/auth/openID.ts with the SFU config
types in a sibling file, takes an options object, and replaces the
MatrixRTC mode with the role we take on the transport plus the session's
slot ID instead of a hard-coded m.call#ROOM.

This changes behaviour: publishers on a livekit_service_url transport
always use the legacy /sfu/get endpoint, so that subscribers can predict
their user:device participant identity, and subscribers always use the
default /get_token endpoint. The MatrixRTC mode no longer influences which
endpoint is used.

src/utils/test.ts

@@ -78,7 +78,7 @@ import {
   type RemoteScreenShareViewModel,
 } from "../state/media/RemoteScreenShareViewModel";
 import { Connection } from "../state/CallViewModel/remoteMembers/Connection";
-import { type SFUConfig } from "../livekit/openIDSFU";
+import { type SFUConfig } from "../livekit/auth";
 
 export function withFakeTimers(continuation: () => void): void {
   vi.useFakeTimers();