新增学习记录功能，拼写验证后自动记录，首页可查看时间线

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

LearnEnglish/LearnEnglish/Models/LearnedStore.swift

@@ -0,0 +1,73 @@
+import Foundation
+
+struct LearnedRecord: Codable {
+    let word: Word
+    let learnedAt: Date
+}
+
+final class LearnedStore {
+    static let shared = LearnedStore()
+    private let key = "learned_records"
+
+    private(set) var records: [LearnedRecord] {
+        didSet {
+            guard let data = try? JSONEncoder().encode(records) else { return }
+            UserDefaults.standard.set(data, forKey: key)
+        }
+    }
+
+    private init() {
+        if let data = UserDefaults.standard.data(forKey: key),
+           let decoded = try? JSONDecoder().decode([LearnedRecord].self, from: data) {
+            records = decoded
+        } else {
+            records = []
+        }
+    }
+
+    func record(_ word: Word) {
+        guard !records.contains(where: { $0.word.id == word.id }) else { return }
+        records.append(LearnedRecord(word: word, learnedAt: Date()))
+    }
+
+    func isRecorded(_ word: Word) -> Bool {
+        records.contains { $0.word.id == word.id }
+    }
+
+    var sectioned: [(title: String, items: [LearnedRecord])] {
+        let sorted = records.sorted { $0.learnedAt > $1.learnedAt }
+        let formatter = DateFormatter()
+        formatter.locale = Locale(identifier: "zh_CN")
+        formatter.dateFormat = "yyyy-MM-dd"
+
+        var groups: [(String, [LearnedRecord])] = []
+        var seen: Set<String> = []
+        for record in sorted {
+            let dateStr = formatter.string(from: record.learnedAt)
+            let title = sectionTitle(dateStr)
+            if !seen.contains(title) {
+                groups.append((title, []))
+                seen.insert(title)
+            }
+            if let index = groups.firstIndex(where: { $0.0 == title }) {
+                groups[index].1.append(record)
+            }
+        }
+        return groups
+    }
+
+    private func sectionTitle(_ dateStr: String) -> String {
+        let today = DateFormatter()
+        today.locale = Locale(identifier: "zh_CN")
+        today.dateFormat = "yyyy-MM-dd"
+        let todayStr = today.string(from: Date())
+        if dateStr == todayStr { return "今天" }
+
+        let calendar = Calendar.current
+        if let yesterday = calendar.date(byAdding: .day, value: -1, to: Date()) {
+            let yesterdayStr = today.string(from: yesterday)
+            if dateStr == yesterdayStr { return "昨天" }
+        }
+        return dateStr
+    }
+}

LearnEnglish/LearnEnglish/Views/CategoryListViewController.swift

@@ -14,6 +14,12 @@ final class CategoryListViewController: UITableViewController {
     override func viewDidLoad() {
         super.viewDidLoad()
         title = "背单词"
+        navigationItem.rightBarButtonItem = UIBarButtonItem(
+            image: UIImage(systemName: "list.bullet.clipboard"),
+            style: .plain,
+            target: self,
+            action: #selector(showHistory)
+        )
         tableView.register(CategoryCardCell.self, forCellReuseIdentifier: "cell")
         tableView.separatorStyle = .none
         tableView.backgroundColor = .systemBackground
@@ -23,6 +29,10 @@ final class CategoryListViewController: UITableViewController {
         }
     }
 
+    @objc private func showHistory() {
+        navigationController?.pushViewController(HistoryViewController(), animated: true)
+    }
+
     private func showError(_ message: String) {
         let label = UILabel()
         label.text = "词库加载失败\n\(message)"

LearnEnglish/LearnEnglish/Views/HistoryViewController.swift

@@ -0,0 +1,71 @@
+import UIKit
+
+final class HistoryViewController: UITableViewController {
+    private let sections: [(title: String, items: [LearnedRecord])]
+
+    init() {
+        sections = LearnedStore.shared.sectioned
+        super.init(style: .insetGrouped)
+    }
+
+    @available(*, unavailable)
+    required init?(coder: NSCoder) { fatalError() }
+
+    override func viewDidLoad() {
+        super.viewDidLoad()
+        title = "学习记录"
+        navigationItem.largeTitleDisplayMode = .never
+        tableView.register(UITableViewCell.self, forCellReuseIdentifier: "cell")
+        tableView.backgroundColor = .systemBackground
+        updateEmptyState()
+    }
+
+    private func updateEmptyState() {
+        if sections.isEmpty {
+            let label = UILabel()
+            label.text = "暂无学习记录"
+            label.textAlignment = .center
+            label.textColor = .secondaryLabel
+            label.font = .preferredFont(forTextStyle: .body)
+            let bg = UIView()
+            bg.addSubview(label)
+            label.translatesAutoresizingMaskIntoConstraints = false
+            NSLayoutConstraint.activate([
+                label.centerXAnchor.constraint(equalTo: bg.centerXAnchor),
+                label.centerYAnchor.constraint(equalTo: bg.centerYAnchor)
+            ])
+            tableView.backgroundView = bg
+        }
+    }
+
+    override func numberOfSections(in tableView: UITableView) -> Int {
+        sections.count
+    }
+
+    override func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
+        sections[section].title
+    }
+
+    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
+        sections[section].items.count
+    }
+
+    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
+        let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath)
+        let record = sections[indexPath.section].items[indexPath.row]
+        var config = cell.defaultContentConfiguration()
+        config.text = record.word.word
+        config.secondaryText = "\(record.word.phonetic)  \(record.word.meaning)"
+        config.image = UIImage(systemName: "text.book.closed")
+        config.imageProperties.tintColor = Theme.Color.accent
+        cell.contentConfiguration = config
+        return cell
+    }
+
+    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
+        Haptics.selection()
+        let record = sections[indexPath.section].items[indexPath.row]
+        let detail = WordDetailViewController(word: record.word, categoryName: "")
+        navigationController?.pushViewController(detail, animated: true)
+    }
+}

LearnEnglish/LearnEnglish/Views/QuizViewController.swift

@@ -357,6 +357,7 @@ final class QuizViewController: UIViewController {
     private func submitSpelling(_ typed: String, for question: QuizQuestion) {
         guard selectedOption == nil else { return }
         selectedOption = typed
+        LearnedStore.shared.record(question.word)
         let correct = typed.lowercased() == question.answer.lowercased()
         if !correct {
             wrongWords.append(question.word)