fixed a bug:translate maybe timeout

ios/OralTrainer/Views/RootView.swift

@@ -649,7 +649,14 @@ struct RootView: View {
         let mediaId = item.id
         chineseTranslationTask = Task {
             do {
-                let map = try await SentenceBoundaryAPI.translateSubtitles(videoHash: mediaId)
+                let expectedIndexes = item.sentences.compactMap { sentence -> Int? in
+                    let text = (sentence.text ?? "").trimmingCharacters(in: .whitespacesAndNewlines)
+                    return text.isEmpty ? nil : sentence.index
+                }
+                let map = try await SentenceBoundaryAPI.loadSubtitles(
+                    videoHash: mediaId,
+                    expectedIndexes: expectedIndexes
+                )
                 guard !Task.isCancelled else { return }
                 await MainActor.run {
                     guard controller.currentItem?.id == mediaId else { return }