fix(storage): reclaim transfer cache and track received files

apple/VniDrop/Core/CoreGateway.swift

@@ -2,6 +2,16 @@ import Foundation
 import Combine
 import VnidropCore
 
+struct CoreStorageUsageModel: Sendable {
+	let blobStoreBytes: UInt64
+	let appDataBytes: UInt64
+}
+
+struct ReceivedArtifactModel: Sendable {
+	let locator: String
+	let logicalSize: UInt64
+}
+
 /// Seam between the feature models and the Rust core, mirroring `CoreGateway`
 /// in the KMP `shared` module. `CoreRepository` is the production implementation;
 /// tests substitute a fake so the models can be exercised without the FFI.
@@ -32,6 +42,8 @@ protocol CoreGateway: AnyObject {
 	func cancel(transferId: UInt64) async -> Result<Void, Error>
 	func delete(transferId: UInt64) async -> Result<Void, Error>
 	func clearReceiveHistory() async -> Result<UInt64, Error>
+	func storageUsage() async -> Result<CoreStorageUsageModel, Error>
+	func receivedArtifacts() async -> Result<[ReceivedArtifactModel], Error>
 	func receiverRequests(transferId: UInt64) async -> Result<[ReceiverRequestModel], Error>
 	func respondReceiverRequest(requestId: String, accepted: Bool, reason: String?) async -> Result<Void, Error>
 	func refresh() async -> Result<Void, Error>