[BOOK-91] fix: enhance auth state validation in AppCoordinator

Author: clxxrlove

src/Projects/BKData/Sources/DataAssembly.swift

@@ -22,8 +22,10 @@ public struct DataAssembly: Assembly {
         container.register(
             type: AuthStateRepository.self
         ) { _ in
+            @Autowired(name: "oauth") var networkProvider: NetworkProvider
             @Autowired var tokenProvider: TokenProvider
             return DefaultAuthStateRepository(
+                networkProvider: networkProvider,
                 tokenProvider: tokenProvider
             )
         }

src/Projects/BKData/Sources/Repository/DefaultAuthStateRepository.swift

@@ -5,9 +5,14 @@ import Combine
 import Foundation
 
 public struct DefaultAuthStateRepository: AuthStateRepository {
+    private let networkProvider: NetworkProvider
     private let tokenProvider: TokenProvider
 
-    public init(tokenProvider: TokenProvider) {
+    public init(
+        networkProvider: NetworkProvider,
+        tokenProvider: TokenProvider
+    ) {
+        self.networkProvider = networkProvider
         self.tokenProvider = tokenProvider
     }
 
@@ -16,8 +21,13 @@ public struct DefaultAuthStateRepository: AuthStateRepository {
             .eraseToAnyPublisher()
     }
 
-    public func accessToken() -> AnyPublisher<String?, Never> {
-        return Just(tokenProvider.accessToken)
-            .eraseToAnyPublisher()
+    public func validate() -> AnyPublisher<Void, AuthError> {
+        networkProvider.request(
+            target: AuthAPI.me,
+            type: EmptyResponse.self
+        )
+        .mapError { _ in AuthError.missingToken }
+        .map { _ in }
+        .eraseToAnyPublisher()
     }
 }

src/Projects/BKDomain/Sources/Interface/Repository/AuthStateRepository.swift

@@ -4,5 +4,5 @@ import Combine
 
 public protocol AuthStateRepository {
     func isLoggedIn() -> AnyPublisher<Bool, Never>
-    func accessToken() -> AnyPublisher<String?, Never>
+    func validate() -> AnyPublisher<Void, AuthError>
 }

src/Projects/BKDomain/Sources/Interface/Usecase/AuthStateUseCase.swift

@@ -4,7 +4,7 @@ import Combine
 import Foundation
 
 /// 인증 상태를 체크합니다.
-/// 단순히 AccessToken 여부를 체크하는 간단한 UseCase로 에러는 방출하지 않습니다.
+/// 내부에 AccessToken이 있는지 확인하고, 서버로 보내 검증합니다.
 public protocol AuthStateUseCase {
-    func execute() -> AnyPublisher<Bool, Never>
+    func execute() -> AnyPublisher<Void, AuthError>
 }

src/Projects/BKDomain/Sources/UseCase/DefaultAuthStateUseCase.swift

@@ -1,5 +1,6 @@
 // Copyright © 2025 Booket. All rights reserved
 
+import BKCore
 import Combine
 import Foundation
 
@@ -10,9 +11,13 @@ public struct DefaultAuthStateUseCase: AuthStateUseCase {
         self.authStateRepository = authStateRepository
     }
 
-    public func execute() -> AnyPublisher<Bool, Never> {
+    public func execute() -> AnyPublisher<Void, AuthError> {
         authStateRepository
             .isLoggedIn()
+            .flatMap { _ in
+                authStateRepository.validate()
+            }
+            .debugError(logger: AppLogger.auth)
             .eraseToAnyPublisher()
     }
 }

src/Projects/BKPresentation/Sources/AppCoordinator.swift

@@ -23,13 +23,15 @@ public final class AppCoordinator: Coordinator {
 
     public func start() {
         authStateUseCase.execute()
-            .sink { [weak self] isLoggedIn in
-                if isLoggedIn {
+            .receive(on: DispatchQueue.main)
+            .sink(receiveCompletion: { [weak self] completion in
+                switch completion {
+                case .finished:
                     self?.startMainFlow()
-                } else {
+                case .failure:
                     self?.startAuthFlow()
                 }
-            }
+            }, receiveValue: { _ in })
             .store(in: &cancellable)
     }