学习记录展示具体学习时间，精确到时分秒

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

LearnEnglish/LearnEnglish/Views/HistoryViewController.swift

@@ -3,6 +3,12 @@ import UIKit
 final class HistoryViewController: UITableViewController {
     private var sections: [(title: String, items: [LearnedRecord])] = []
     private var speechObserver: NSObjectProtocol?
+    private let timeFormatter: DateFormatter = {
+        let f = DateFormatter()
+        f.locale = Locale(identifier: "zh_CN")
+        f.dateFormat = "HH:mm:ss"
+        return f
+    }()
 
     init() {
         super.init(style: .plain)
@@ -73,7 +79,8 @@ final class HistoryViewController: UITableViewController {
     override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
         let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! WordCardCell
         let record = sections[indexPath.section].items[indexPath.row]
-        cell.configure(with: record.word, count: record.count, accuracy: record.accuracy)
+        let time = timeFormatter.string(from: record.learnedAt)
+        cell.configure(with: record.word, count: record.count, accuracy: record.accuracy, time: time)
         cell.onSpeak = { word in
             SpeechService.shared.speak(word.word)
         }

LearnEnglish/LearnEnglish/Views/WordCardCell.swift

@@ -92,9 +92,9 @@ final class WordCardCell: UITableViewCell {
         updateSpeakerState()
     }
 
-    func configure(with word: Word, count: Int, accuracy: Int) {
+    func configure(with word: Word, count: Int, accuracy: Int, time: String) {
         configure(with: word)
-        countLabel.text = "\(count)次 · \(accuracy)%"
+        countLabel.text = "\(count)次 · \(accuracy)% · \(time)"
         countLabel.isHidden = false
     }
 

LearnEnglish/LearnEnglish/Views/WordHistoryViewController.swift

@@ -118,7 +118,7 @@ final class WordHistoryViewController: UIViewController {
 
         let formatter = DateFormatter()
         formatter.locale = Locale(identifier: "zh_CN")
-        formatter.dateFormat = "yyyy-MM-dd HH:mm"
+        formatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
         let dateLabel = UILabel()
         dateLabel.text = "最近学习：\(formatter.string(from: record.learnedAt))"
         dateLabel.font = .preferredFont(forTextStyle: .caption1)