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/settings/widgets/usb_import_panel.dart

@@ -1,6 +1,7 @@
 import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 
+import '../../../core/localization/app_localizations.dart';
 import '../../../core/theme/app_theme.dart';
 import '../../../shared/services/toast_service.dart';
 import '../services/usb_detection_service.dart';
@@ -21,18 +22,20 @@ class _UsbImportPanelState extends ConsumerState<UsbImportPanel> {
   Future<void> _detect() async {
     if (_detecting) return;
     setState(() => _detecting = true);
+    final l10n = AppLocalizations.of(context);
     final connected = await UsbDetectionService.instance.detectUsb();
     if (!mounted) return;
     setState(() => _detecting = false);
     if (connected) {
-      ToastService.showInfo(context, '正在检测U盘...');
+      ToastService.showInfo(context, l10n?.detectingUsb ?? '正在检测U盘...');
     } else {
-      ToastService.showWarning(context, '未检测到U盘');
+      ToastService.showWarning(context, l10n?.usbNotDetected ?? '未检测到U盘');
     }
   }
 
   @override
   Widget build(BuildContext context) {
+    final l10n = AppLocalizations.of(context);
     final state = ref.watch(_usbStateProvider);
     final connected = state.maybeWhen(
       data: (s) => s.isConnected,
@@ -67,7 +70,7 @@ class _UsbImportPanelState extends ConsumerState<UsbImportPanel> {
                   const SizedBox(width: 12),
                   Expanded(
                     child: Text(
-                      connected ? 'U盘已连接' : '未检测到U盘',
+                      connected ? (l10n?.usbConnected ?? 'U盘已连接') : (l10n?.usbNotDetected ?? '未检测到U盘'),
                       style: TextStyle(
                         color: AppTheme.textPrimary,
                         fontSize: 16,
@@ -80,8 +83,8 @@ class _UsbImportPanelState extends ConsumerState<UsbImportPanel> {
               const SizedBox(height: 12),
               Text(
                 connected
-                    ? '挂载路径: ${path ?? "未知"}'
-                    : '请插入U盘后点击"重新检测"',
+                    ? '${l10n?.mountPath ?? '挂载路径'}: ${path ?? "?"}'
+                    : (l10n?.insertUsb ?? '请插入U盘后重试'),
                 style: TextStyle(
                     color: AppTheme.textSecondary, fontSize: 13),
               ),
@@ -98,13 +101,13 @@ class _UsbImportPanelState extends ConsumerState<UsbImportPanel> {
                             child: CircularProgressIndicator(strokeWidth: 2),
                           )
                         : const Icon(Icons.refresh, size: 18),
-                    label: const Text('重新检测'),
+                    label: Text(l10n?.reDetect ?? '重新检测'),
                   ),
                   const SizedBox(width: 12),
                   ElevatedButton.icon(
                     onPressed: connected ? () => _import(path) : null,
                     icon: const Icon(Icons.download, size: 18),
-                    label: const Text('导入程序'),
+                    label: Text(l10n?.importProgram ?? '导入程序'),
                   ),
                 ],
               ),
@@ -123,7 +126,7 @@ class _UsbImportPanelState extends ConsumerState<UsbImportPanel> {
             crossAxisAlignment: CrossAxisAlignment.start,
             children: [
               Text(
-                '使用说明',
+                l10n?.usageInstructions ?? '使用说明',
                 style: TextStyle(
                   color: AppTheme.textPrimary,
                   fontSize: 14,
@@ -131,9 +134,9 @@ class _UsbImportPanelState extends ConsumerState<UsbImportPanel> {
                 ),
               ),
               const SizedBox(height: 8),
-              _bullet('将程序文件 (.json) 放入 U盘根目录的 programs 文件夹'),
-              _bullet('插入 U盘后点击"重新检测"'),
-              _bullet('检测成功后点击"导入程序"加载程序列表'),
+              _bullet(l10n?.usbUsageStep1 ?? '将程序文件 (.json) 放入 U盘根目录的 programs 文件夹'),
+              _bullet(l10n?.usbUsageStep2 ?? '插入 U盘后点击"重新检测"'),
+              _bullet(l10n?.usbUsageStep3 ?? '检测成功后点击"导入程序"加载程序列表'),
             ],
           ),
         ),
@@ -142,11 +145,12 @@ class _UsbImportPanelState extends ConsumerState<UsbImportPanel> {
   }
 
   void _import(String? path) {
+    final l10n = AppLocalizations.of(context);
     if (path == null) {
-      ToastService.showWarning(context, 'U盘路径无效');
+      ToastService.showWarning(context, l10n?.usbPathInvalid ?? 'U盘路径无效');
       return;
     }
-    ToastService.showInfo(context, '正在导入程序...');
+    ToastService.showInfo(context, l10n?.importingPrograms ?? '正在导入程序...');
     // TODO: 接入 program_import_service 实现真正的导入流程
   }