feat: add sample-app-voip with CometChat Push Notifications VoIP

[ashfaqcometchat]

New

• Added a new sample-app-voip showcasing VoIP push notification integration using com.cometchat:push-notifications-android:1.0.0-beta.1.
• Added support for incoming calls via push notifications when the app is running in the background or has been terminated, with a built-in incoming call screen provided by the library.
• Added foreground incoming call handling using CometChat.CallListener with a custom IncomingCallActivity, matching the experience provided in sample-app-ringing.
• Added intelligent FCM payload routing to prevent duplicate incoming call screens by skipping call push handling while the app is active in the foreground.
• Added CallAnsweredHandler support to accept calls on the server and launch the ongoing call screen from background or killed app states.
• Added an outgoing call flow with ringing screen support and call cancellation handling.
• Added an ongoing call screen with audio and video calling support powered by the CometChat Calls SDK.
• Added a user list with search, pagination, and quick-access audio/video calling actions.
• Added call logs with pull-to-refresh support for easier call history management.
• Added a dynamic credentials configuration screen for entering App ID, Auth Key, and Region values at runtime.
• Added centralized SDK initialization for Chat SDK, Calls SDK, and Push Notifications SDK within Application.onCreate() for reliable cold-start handling.
• Added automatic FCM token registration after login and token unregistration before logout.
• Added token rotation handling using handleTokenRefresh() within onNewToken to ensure uninterrupted push notification delivery.
• Added support for Kotlin 2.2.0 and compileSdk 36 to maintain compatibility with the push notifications library.

Enhancements

• None

Fixes

• None