fix(realtime): Swift 6 Sendable fixes for RealtimeClientV2 and tests

- Constrain lifecycleManager to Sendable & AnyObject to satisfy Swift 6
  strict concurrency in RealtimeClientV2
- Add @unchecked Sendable to RealtimeChannelBroadcastTests (Task closure
  captures self implicitly)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: grdsdev

Sources/Realtime/RealtimeClientV2.swift

@@ -64,7 +64,7 @@ public final class RealtimeClientV2: Sendable, RealtimeClientProtocol {
     /// Retains the optional app-lifecycle observer for the client's lifetime.
     /// Stored as `AnyObject?` so this type remains available on platforms where
     /// the concrete `RealtimeLifecycleManager` is not compiled.
-    var lifecycleManager: AnyObject?
+    var lifecycleManager: (any Sendable & AnyObject)?
 
     /// Whether the socket was `.connected` the last time the app entered the
     /// background. `handleAppForeground` only attempts recovery when this is

Tests/RealtimeTests/RealtimeChannelBroadcastTests.swift

@@ -21,7 +21,7 @@ import XCTest
 #else
 
   @available(macOS 13.0, iOS 16.0, watchOS 9.0, tvOS 16.0, *)
-  final class RealtimeChannelBroadcastTests: XCTestCase {
+  final class RealtimeChannelBroadcastTests: XCTestCase, @unchecked Sendable {
     let url = URL(string: "http://localhost:54321/realtime/v1")!
     let apiKey = "publishable.api.key"