[BOOK-365] fix: resolve DI violation

Author: clxxrlove

src/Projects/BKStorage/Sources/TokenStorage/KeychainPushTokenStore.swift

@@ -6,6 +6,9 @@ import BKData
 public struct KeychainPushTokenStore: PushTokenStore {
     private let storage: KeyValueStorage
 
+    /// AppDelegate에서 DI 없이 사용할 수 있도록 shared instance 제공
+    public static let shared = KeychainPushTokenStore(storage: KeychainKeyValueStorage())
+
     public init(storage: KeyValueStorage) {
         self.storage = storage
     }

src/Projects/Booket/Sources/AppDelegate.swift

@@ -62,17 +62,17 @@ final class AppDelegate: UIResponder, UIApplicationDelegate {
         didReceiveRegistrationToken fcmToken: String?
     ) {
         guard let token = fcmToken else { return }
-        let storage = KeychainKeyValueStorage()
-        let pushTokenStore = KeychainPushTokenStore(storage: storage)
 
-        pushTokenStore.save(fcmToken: token)
+        KeychainPushTokenStore.shared.save(fcmToken: token)
             .sink(
                 receiveCompletion: { completion in
                     if case .failure(let error) = completion {
                         AppLogger.auth.error("Failed to save FCM token: \(error)")
                     }
                 },
-                receiveValue: { _ in }
+                receiveValue: { _ in
+                    AppLogger.auth.info("FCM token saved successfully")
+                }
             )
             .store(in: &cancellables)
     }