Android calls: single-source ring (fix double-ring), drop battery dialog, add wake logging

On-device (OnePlus, build 5cb3d0c): new ring UI confirmed; backgrounded rang
twice (channel sound + activity ringtone, and both wake paths raised it);
battery dialog deemed unprofessional (WhatsApp/Teams don't prompt it).

- Double-ring: notification channel is now SILENT (new id bzc_incoming_calls_v2,
  no sound/vibration, onlyAlertOnce) so IncomingCallActivity is the single ring
  source (looping ringtone + vibrator). showIncoming dedups atomically
  (if(!active.add(uuid)) return) so the FCM push and WebSocket paths can't both
  ring the same call.
- Battery dialog removed: dropped requestCallReliability (web call + plugin
  method) and REQUEST_IGNORE_BATTERY_OPTIMIZATIONS permission.
- Logging: Log.i(bzcall, ...) across the wake chain to diagnose swiped-away
  (OnePlus force-kills on swipe and blocks FCM cold-start).

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

server/public/home.html

@@ -4350,9 +4350,6 @@ async function setupNativeCall(){
     // token is already registered by setupNativePush — the server call-wake targets it, so no token step here.
     if(!cfg || !cfg.androidCall){ console.log('[nativecall] Android native calling disabled by server — using WebView calls'); return; }
     _callkitReady=true; _callWebViewMedia=true;
-    // Ask for a battery-optimization exemption so a killed/Dozing phone still gets the high-priority FCM
-    // call-wake in time to ring (OnePlus/Oppo hold it otherwise). Prompt only the first time; then just check.
-    try{ if(NC.requestCallReliability){ const asked=localStorage.getItem('bzcCallRelAsked'); const rel=await NC.requestCallReliability({ prompt: !asked }); localStorage.setItem('bzcCallRelAsked','1'); if(rel && rel.ignoringBatteryOptimizations===false) console.log('[nativecall] app is NOT exempt from battery optimization — killed-state ring may be delayed until this is allowed'); } }catch(_){}
   } else {
     // iOS CallKit: native media (the plugin owns this identity's one LiveKit connection). Flipped on once native
     // media carries the audio.