feat: 定义仓库协议与用例（含会话）

IosClientKit/Sources/CoreDomain/SessionUseCase.swift

@@ -0,0 +1,24 @@
+/// 会话用例。
+public struct SessionUseCase: Sendable {
+    private let repository: SessionRepository
+
+    public init(repository: SessionRepository) {
+        self.repository = repository
+    }
+
+    public func observeIsLoggedIn() -> AsyncThrowingStream<Bool, Error> {
+        repository.observeIsLoggedIn()
+    }
+
+    public func requestSmsCode(phone: String) async throws {
+        try await repository.requestSmsCode(phone: phone)
+    }
+
+    public func login(phone: String, code: String) async throws {
+        try await repository.login(phone: phone, code: code)
+    }
+
+    public func logout() async throws {
+        try await repository.logout()
+    }
+}