When another user starts a call in a DM room, show a fixed-position
notification with caller avatar, name, and Answer/Decline buttons.
A Web Audio API double-pulse ring tone plays until answered, declined,
or the 30-second auto-dismiss fires.
- useIncomingDmCall hook: listens to MatrixRTC SessionStarted/SessionEnded,
filters DM rooms (encrypted, ≤2 members), auto-dismisses after 30s,
stops if caller leaves or user joins another call
- IncomingCallNotification component: ring tone, caller info, themed UI
for LotusGuild Terminal TDS (navy bg, orange border, neon-green Answer)
and standard Cinny dark/light (CSS vars, folds Button Success/Critical)
- Router.tsx: mount IncomingCallNotification inside CallEmbedProvider
root