feat(calls): CallKit kill-switch + fix ~1s re-ring on cancel

MIC BROKEN with CallKit: a CallKit call reserves the microphone, so the WebView's
WebRTC can't capture it — calls are unusable until native LiveKit media lands. Add a
server kill-switch (CALLKIT_ENABLED, default OFF) so CallKit can be flipped without an
app rebuild: /api/meetings/config now returns callkit; setupNativeCall bails when off
(-> WebView calls, mic works); push.js only sends VoIP/CallKit pushes when enabled.
Deploying with the flag unset immediately restores working WebView calls.

RE-RING: a late cancel push for an already-declined call hit the plugin's 'unknown
uuid' path and re-reported a fresh incoming call (~1s re-ring). Track endedCalls and
make a late cancel for an already-ended call a no-op.

Server part deploys now (no rebuild); plugin re-ring fix ships with the native build.

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

mobile/plugins/native-call/ios/Sources/NativeCallPlugin/NativeCallPlugin.swift

@@ -36,6 +36,8 @@ public class NativeCallPlugin: CAPPlugin, CAPBridgedPlugin, PKPushRegistryDelega
     private var voipToken: String = ""
     // callUUID -> the call's data (room, kind, callerId, …) so answer/end can hand it back to JS.
     private var calls: [UUID: [String: Any]] = [:]
+    // Calls we've already ended locally — so a LATE cancel push doesn't re-report (which briefly re-rang).
+    private var endedCalls = Set<UUID>()
 
     override public func load() {
         let config = CXProviderConfiguration(localizedName: "Biz Connect")
@@ -98,6 +100,7 @@ public class NativeCallPlugin: CAPPlugin, CAPBridgedPlugin, PKPushRegistryDelega
     private func requestEnd(_ uuid: UUID) {
         callController.request(CXTransaction(action: CXEndCallAction(call: uuid))) { _ in }
         calls.removeValue(forKey: uuid)
+        endedCalls.insert(uuid)
     }
 
     // MARK: - PushKit (VoIP)
@@ -125,10 +128,16 @@ public class NativeCallPlugin: CAPPlugin, CAPBridgedPlugin, PKPushRegistryDelega
             if calls[uuid] != nil {
                 provider?.reportCall(with: uuid, endedAt: Date(), reason: .remoteEnded)
                 calls.removeValue(forKey: uuid)
+                endedCalls.insert(uuid)
+                completion()
+            } else if endedCalls.contains(uuid) {
+                // Already ended locally (we declined/hung up) — do NOT re-report; that caused the ~1s re-ring.
                 completion()
             } else {
+                // Never saw the invite — iOS still requires a reported call for this push, so report then end.
                 let u = CXCallUpdate()
                 u.remoteHandle = CXHandle(type: .generic, value: "Call")
+                endedCalls.insert(uuid)
                 provider?.reportNewIncomingCall(with: uuid, update: u) { [weak self] _ in
                     self?.provider?.reportCall(with: uuid, endedAt: Date(), reason: .remoteEnded)
                     completion()
@@ -158,6 +167,7 @@ public class NativeCallPlugin: CAPPlugin, CAPBridgedPlugin, PKPushRegistryDelega
 
     public func providerDidReset(_ provider: CXProvider) {
         calls.removeAll()
+        endedCalls.removeAll()
     }
 
     public func provider(_ provider: CXProvider, perform action: CXAnswerCallAction) {
@@ -172,6 +182,7 @@ public class NativeCallPlugin: CAPPlugin, CAPBridgedPlugin, PKPushRegistryDelega
         data["callUUID"] = action.callUUID.uuidString
         notifyListeners("endCall", data: data)
         calls.removeValue(forKey: action.callUUID)
+        endedCalls.insert(action.callUUID)
         action.fulfill()
     }