fix: mark CNContactStore as nonisolated for Swift 6 concurrency

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: cyberpapiii

swift/Sources/iMessageMax/Contacts/ContactResolver.swift

@@ -5,7 +5,9 @@ import Foundation
 actor ContactResolver {
     private var cache: [String: String] = [:]  // handle -> name
     private var isInitialized = false
-    private let store = CNContactStore()
+    // CNContactStore is not Sendable, so we mark it nonisolated(unsafe)
+    // This is safe because we only use it from within actor-isolated methods
+    nonisolated(unsafe) private let store = CNContactStore()
 
     // MARK: - Authorization