Native calls: upgrade to LiveKit 2.15 + add CallKit audio-session coordination

Root cause of the intermittent dead-mic / no-audio / late-speaker: LiveKit's
automatic AVAudioSession config races CallKit's activation. The fix needs the
2.15+ audio API, which the build wasn't getting ('~> 2.0' resolved an older 2.x
from a stale spec cache). So:
- NativeCall.podspec: pin LiveKitClient '~> 2.15'.
- codemagic.yaml: 'pod install --repo-update' so the spec repo knows 2.15.x.
- Plugin: disable LiveKit auto audio-session config + keep the engine OFF; in
  CXProvider didActivate set the session category and enable the engine; in
  didDeactivate disable it. Request mic permission on connect so enabling the
  engine in didActivate doesn't block on undetermined permission.

All AudioManager APIs verified against the raw 2.15.3 source (setEngineAvailability,
AudioEngineAvailability.default/.none, audioSession.isAutomaticConfigurationEnabled).

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

codemagic.yaml

@@ -93,7 +93,9 @@ workflows:
       - name: Install CocoaPods
         script: |
           cd mobile/ios/App
-          pod install
+          # --repo-update refreshes the CocoaPods spec repo so it knows the latest LiveKitClient (the build box's
+          # cached spec repo was stale, so '~> 2.x' resolved an OLD version missing the CallKit audio API).
+          pod install --repo-update
 
       - name: Build the signed IPA
         script: |