chore: updated CXProvider init and config flow (#2326)

### 💡 Overview

Avoided CXProvider redundant recreation. 
Updated CXProvider configuration setup.

🎫 Ticket:
https://linear.app/stream/issue/RN-414/cxprovider-instantiation-and-configuration-updates


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

## Summary by CodeRabbit

* **Bug Fixes**
* Improved call setup reliability by consistently applying the latest
call configuration before creating and starting calls.
* Fixed settings handling with a safer in-memory cache to improve
reliability across app sessions.
* Reduced issues from concurrent settings access to help prevent
inconsistent behavior.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: greenfrvr

packages/react-native-callingx/ios/CallingxImpl.swift

@@ -108,6 +108,8 @@ import stream_react_native_webrtc
         if CallingxImpl.sharedProvider == nil {
             CallingxImpl.sharedProvider = CXProvider(configuration: Settings.getProviderConfiguration())
         }
+      
+        callKeepCallController = CXCallController()
 
         callKeepProvider = CallingxImpl.sharedProvider
         callKeepProvider?.setDelegate(nil, queue: nil)
@@ -128,7 +130,8 @@ import stream_react_native_webrtc
 
     // MARK: - Class Methods
     @objc public static func initializeIfNeeded() {
-        _ = getSharedInstance() // ensures the shared instance is created and CXProvider delegate is set        
+        _ = getSharedInstance() // ensures the shared instance is created and CXProvider delegate is set
+        CallingxImpl.sharedProvider?.configuration = Settings.getProviderConfiguration()
     }
 
     @objc public static func reportNewIncomingCall(
@@ -379,29 +382,8 @@ import stream_react_native_webrtc
 
     // MARK: - Setup Methods
     @objc public func setup(options: [String: Any]) {
-        callKeepCallController = CXCallController()
-
         Settings.setSettings(options)
-
-        // This is mostly needed for very first setup, as we need to override the default
-        // provider configuration which is set in the constructor.
-        // IMPORTANT: We override the CXProvider instance only when there are no calls in
-        // flight, otherwise we'd destroy CallKit state/events for a live call. We check our
-        // own storage rather than CXCallObserver here: the observer trails registration and
-        // can briefly report empty (e.g. a VoIP-push call reported just before setup runs),
-        // which would wrongly tear down the provider mid-call.
-        if (CallingxImpl.uuidStorage?.count() ?? 0) == 0 {
-            let oldProvider = CallingxImpl.sharedProvider
-            let newProvider = CXProvider(configuration: Settings.getProviderConfiguration())
-            newProvider.setDelegate(self, queue: nil)
-
-            CallingxImpl.sharedProvider = newProvider
-            callKeepProvider = newProvider
-
-            oldProvider?.setDelegate(nil, queue: nil)
-            oldProvider?.invalidate()
-        }
-
+        CallingxImpl.sharedProvider?.configuration = Settings.getProviderConfiguration()
         isSetup = true
     }
 
@@ -615,10 +597,13 @@ import stream_react_native_webrtc
           return
         }
 
+        CallingxImpl.sharedProvider?.configuration = Settings.getProviderConfiguration()
+      
         let call = storage.getOrCreateCall(forCid: callId, isOutgoing: true)
         call.markStartedConnecting() // outgoing: will be reported via reportOutgoingCall(startedConnectingAt:)
 
-        let handleType = Settings.getHandleType("generic")
+        let handleTypeString = Settings.getSettings()["handleType"] as? String
+        let handleType = Settings.getHandleType(handleTypeString ?? "generic")
         let callHandle = CXHandle(type: handleType, value: phoneNumber)
         let startCallAction = CXStartCallAction(call: call.uuid, handle: callHandle)
         startCallAction.isVideo = hasVideo

packages/react-native-callingx/ios/Settings.swift

@@ -5,23 +5,36 @@ import UIKit
 @objcMembers public class Settings: NSObject {
     private static let settingsKey = "CallingxSettings"
 
+    // In-memory cache of the settings dictionary
+    private static var cachedSettings: [String: Any]?
+    private static let cacheQueue = DispatchQueue(label: "io.getstream.callingx.settings")
+
     public static func getSettings() -> [String: Any] {
-        return UserDefaults.standard.dictionary(forKey: settingsKey) ?? [:]
+        return cacheQueue.sync {
+            if let cached = cachedSettings {
+                return cached
+            }
+            cachedSettings = UserDefaults.standard.dictionary(forKey: settingsKey) ?? [:]
+            return cachedSettings!
+        }
     }
 
     public static func setSettings(_ options: [String: Any]?) {
         CallingxLog.settings.debugPublic("[setSettings] options = \(String(describing: options))")
 
-        var settings: [String: Any] = getSettings()
+        cacheQueue.sync {
+            // Load lazily here rather than via getSettings() to avoid re-entrant sync on cacheQueue.
+            var settings = cachedSettings ?? UserDefaults.standard.dictionary(forKey: settingsKey) ?? [:]
 
-        if let options = options {
-            for (key, value) in options {
-                settings[key] = value
+            if let options = options {
+                for (key, value) in options {
+                    settings[key] = value
+                }
             }
-        }
 
-        UserDefaults.standard.set(settings, forKey: settingsKey)
-        UserDefaults.standard.synchronize()
+            cachedSettings = settings
+            UserDefaults.standard.set(settings, forKey: settingsKey)
+        }
     }
 
     public static func getShouldRejectCallWhenBusy() -> Bool {