Content Scanner Service (#5826)

* implemented the content scanner service with caching and a way to use in the state store context

* fix swiftformat comment enforcing

* pr suggestions

ElementX/Sources/Services/ContentScanner/ContentScannerServiceProtocol.swift

@@ -0,0 +1,27 @@
+//
+// Copyright 2026 Element Creations Ltd.
+//
+// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+// Please see LICENSE files in the repository root for full details.
+//
+
+import Foundation
+
+enum ContentScannerServiceError: Error {
+    case failedScanning
+}
+
+// sourcery: AutoMockable
+/// Scans media sources through the content scanner, caching the verdicts by URL so that each source
+/// is only ever scanned once. Mirrors ``MediaProviderProtocol``'s shape: a synchronous cache lookup
+/// for views that already have a verdict and an async method to perform the scan.
+nonisolated protocol ContentScannerServiceProtocol: Sendable {
+    /// The cached scan verdict for the given source: `true` when the content is safe, `false` when
+    /// it is unsafe, or `nil` when the source hasn't been scanned yet.
+    func scanResultFromSource(_ source: MediaSourceProxy) -> Bool?
+    
+    /// Starts a scan for the given source unless there's already a cached verdict, in which case
+    /// that is returned. Failed scans aren't cached so that they can be retried.
+    @discardableResult
+    func loadScanResultFromSource(_ source: MediaSourceProxy) async -> Result<Bool, ContentScannerServiceError>
+}