Root cause: sendToFederatedCallUsers used sendToDmMembers when dmChannelId
was set, which broadcast to ALL DM members including the caller's replicated
stub. The caller's multi-instance WS received dm_call_accepted with the
REMOTE instance's dmChannelId, causing token request for a non-existent
channel (403) and preventing the caller from connecting.
Fix 1: sendToFederatedCallUsers always uses ringedUserIds (exact recipients)
instead of sendToDmMembers (all members including caller stub).
Fix 2: dm_call_accepted handler only sets activeDmCall if the client is the
caller (wasOutgoingCall) or already connected to LiveKit. Other instances of
the same user just clear ringing without entering stuck "Connecting..." state.
Jannis Braun
86fe713a7c