call: stop the ring on a user's other devices when one answers (answered-elsewhere)

A user signed in on two devices (iPhone + Android) rang on both. When they
answered on Android, the iPhone kept ringing: markDmAnswered only emitted a
WS 'call-taken', which never reaches a backgrounded/killed device ringing on
CallKit (no live socket).

Now markDmAnswered also pushes a native cancel to the answerer's OTHER
devices. The device that actually answered is skipped via exceptToken (its own
call-push token) — critical on iOS, where a cancel would end the just-answered
CallKit call; Android's cancel branch never tears down a live call anyway.

- push.sendCallCancel(userId, uuid, { exceptToken, reason }) — skips the
  answering device's token; existing 2-arg callers unchanged.
- calls.markDmAnswered(room, userId, exceptToken) — fires the cancel.
- POST /api/calls/answered now takes deviceToken.
- home.html: the native answerCall handler POSTs /api/calls/answered with this
  device's own token (ios-voip or fcm), so native/LiveKit calls (which bypass
  the mesh) are marked answered and siblings stop ringing.

Server + web only — no native build needed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/public/home.html

@@ -4337,6 +4337,7 @@ async function unsubscribePush(){
 let _callkitReady=false;
 let _callWebViewMedia=false; // Android Increment 1: native full-screen ring, but MEDIA stays in the WebView (iOS runs the call media natively via the plugin). Governs the answer/outgoing branches below.
 let _nativeAnswered=new Set(); // rooms this device answered natively (so a "call-taken" from the server doesn't end our own call)
+let _myVoipTok=''; // this device's own iOS VoIP (ios-voip) token — sent on answer so the answered-elsewhere cancel skips us
 function nativeCallPlugin(){ const P=window.Capacitor&&window.Capacitor.Plugins; return (P&&P.NativeCall)||null; }
 function nativeCallOn(){ return _callkitReady; }
 async function setupNativeCall(){
@@ -4356,8 +4357,8 @@ async function setupNativeCall(){
     if(!cfg || !cfg.callkit){ console.log('[callkit] disabled by server — using WebView calls'); return; }
     _callkitReady=true;
     // VoIP (PushKit) token → register as an 'ios-voip' device so the server sends CallKit wake pushes.
-    NC.addListener('voipToken', (e)=>{ const token=e&&e.token; if(!token) return; postJSON('/api/v1/devices',{ platform:'ios-voip', token }).then(()=>console.log('[callkit] voip token registered')).catch((err)=>console.warn('[callkit] voip register failed', err)); });
-    try{ const t=await NC.getToken(); if(t&&t.token) postJSON('/api/v1/devices',{ platform:'ios-voip', token:t.token }).catch(()=>{}); }catch(_){}
+    NC.addListener('voipToken', (e)=>{ const token=e&&e.token; if(!token) return; _myVoipTok=token; postJSON('/api/v1/devices',{ platform:'ios-voip', token }).then(()=>console.log('[callkit] voip token registered')).catch((err)=>console.warn('[callkit] voip register failed', err)); });
+    try{ const t=await NC.getToken(); if(t&&t.token){ _myVoipTok=t.token; postJSON('/api/v1/devices',{ platform:'ios-voip', token:t.token }).catch(()=>{}); } }catch(_){}
   }
   // Native media: the plugin carries the call over its OWN LiveKit room. The WebView must NOT also join
   // (LiveKit = one connection per identity). So on answer we do NOT enterMeeting — we just tell the server
@@ -4366,6 +4367,11 @@ async function setupNativeCall(){
   NC.addListener('answerCall', (d)=>{ try{
     if(!d||!d.room) return;
     _nativeAnswered.add(d.room);
+    // Tell the server THIS device answered. Native/LiveKit calls bypass our mesh, so without this the call is
+    // never marked answered server-side and the answerer's OTHER devices (e.g. an iPhone ringing on CallKit)
+    // keep ringing. deviceToken = our own call token so the answered-elsewhere cancel skips us (never ends the
+    // call we just picked up). iOS → the VoIP token; Android → the FCM token.
+    try{ const _ct=(nativePlatform()==='ios')?_myVoipTok:_nativeTok; postJSON('/api/calls/answered',{ room:d.room, deviceToken:_ct||'' }).catch(()=>{}); }catch(_){}
     dismissCallInvite(d.room);
     // Open the REAL meeting window. Joining the mesh marks the call answered server-side, shows the caller's
     // tile, and wires the end-both-sides lifecycle. meetReturn = the chat to land back on when the call ends.