feat: track settings changes and enforce Chinese UI copy

app/gui/main_window.py

@@ -27,6 +27,9 @@ class MainWindow(QMainWindow):
         )
         self.setWindowTitle("cmshopee")
         self.resize(1180, 760)
+        self._settings_tab_index = TAB_TITLES.index("⑤ 设置")
+        self._last_tab_index = 0
+        self._reverting_tab_change = False
         self.tabs = QTabWidget()
         self.tabs.setObjectName("mainTabs")
         self.tabs.setStyleSheet(TAB_STYLE)
@@ -82,8 +85,52 @@ class MainWindow(QMainWindow):
                 widget.refresh_tasks()
 
     def _on_tab_changed(self, index):
+        if self._reverting_tab_change:
+            self._last_tab_index = index
+            self.statusBar().showMessage(f"当前：{self.tabs.tabText(index)}")
+            return
+        previous = self._last_tab_index
+        if previous == self._settings_tab_index and index != previous:
+            if not self._confirm_leave_settings_tab():
+                self._reverting_tab_change = True
+                try:
+                    self.tabs.setCurrentIndex(previous)
+                finally:
+                    self._reverting_tab_change = False
+                self._last_tab_index = previous
+                self.statusBar().showMessage(f"当前：{self.tabs.tabText(previous)}")
+                return
+        self._last_tab_index = index
         self.statusBar().showMessage(f"当前：{self.tabs.tabText(index)}")
 
+    def _settings_tab(self):
+        return self.tabs.widget(self._settings_tab_index)
+
+    def _confirm_leave_settings_tab(self):
+        settings_tab = self._settings_tab()
+        if not hasattr(settings_tab, "is_dirty") or not settings_tab.is_dirty():
+            return True
+        box = QMessageBox(self)
+        box.setWindowTitle("未保存更改")
+        box.setText("⑤ 设置有未保存更改。要先保存再离开吗？")
+        save_button = box.addButton("保存", QMessageBox.AcceptRole)
+        discard_button = box.addButton("放弃", QMessageBox.DestructiveRole)
+        cancel_button = box.addButton("取消", QMessageBox.RejectRole)
+        box.setDefaultButton(save_button)
+        box.exec()
+        clicked = box.clickedButton()
+        if clicked is save_button:
+            return bool(settings_tab.save_app_settings())
+        if clicked is discard_button:
+            return bool(settings_tab.discard_unsaved_changes())
+        return False
+
+    def closeEvent(self, event):
+        if self._confirm_leave_settings_tab():
+            event.accept()
+            return
+        event.ignore()
+
     def open_accounts_tab(self):
         self.tabs.setCurrentIndex(TAB_TITLES.index("④ 账号管理"))