feat(i18n): 完成全量 UI 文本国际化，替换所有硬编码中文为 AppLocalizations 调用

- core/localization: 新增约 60 个翻译键（含参数化方法），中英双语覆盖
- shared/widgets: CommonDialog 默认参数国际化
- features/home: 完成页操作步骤指引、状态栏串口连接状态、程序列表状态标签
- features/programs: 表头状态列、表单验证提示、导入/模板操作反馈、删除确认（参数化）
- features/program_detail: 步骤列表/表单标题、删除确认、速度档位显示（参数化）
- features/device: run_state_provider 错误消息改为错误码
- features/settings: 升级页、密码面板、语言面板、U盘导入面板、串口配置面板全部替换

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

lib/features/home/widgets/status_bar.dart

@@ -263,13 +263,14 @@ class _SerialConnectionIndicator extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    final l10n = AppLocalizations.of(context);
     final connected = state == SerialConnectionState.connected;
     final connecting = state == SerialConnectionState.connecting;
     final text = connected
-        ? '已连接'
+        ? (l10n?.serialConnected ?? '已连接')
         : connecting
-            ? '连接中'
-            : '未连接';
+            ? (l10n?.serialConnecting ?? '连接中')
+            : (l10n?.serialDisconnected ?? '未连接');
     final color = connected
         ? AppTheme.statusRunning
         : connecting