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/password_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/settings_service.dart';
@@ -33,20 +34,21 @@ class _PasswordPanelState extends ConsumerState<PasswordPanel> {
 
   Future<void> _submit() async {
     if (_submitting) return;
+    final l10n = AppLocalizations.of(context);
     final oldPwd = _oldCtrl.text.trim();
     final newPwd = _newCtrl.text.trim();
     final confirmPwd = _confirmCtrl.text.trim();
 
     if (oldPwd.isEmpty || newPwd.isEmpty || confirmPwd.isEmpty) {
-      setState(() => _error = '请填写所有字段');
+      setState(() => _error = l10n?.fillAllFields ?? '请填写所有字段');
       return;
     }
     if (newPwd.length < 6) {
-      setState(() => _error = '新密码至少6位字符');
+      setState(() => _error = l10n?.newPwdMinLength ?? '新密码至少6位字符');
       return;
     }
     if (newPwd != confirmPwd) {
-      setState(() => _error = '两次输入的新密码不一致');
+      setState(() => _error = l10n?.passwordMismatch ?? '两次输入的新密码不一致');
       return;
     }
 
@@ -60,7 +62,7 @@ class _PasswordPanelState extends ConsumerState<PasswordPanel> {
       if (!mounted) return;
       setState(() {
         _submitting = false;
-        _error = '原密码错误';
+        _error = l10n?.oldPasswordError ?? '原密码错误';
       });
       return;
     }
@@ -73,14 +75,15 @@ class _PasswordPanelState extends ConsumerState<PasswordPanel> {
       _oldCtrl.clear();
       _newCtrl.clear();
       _confirmCtrl.clear();
-      ToastService.showSuccess(context, '密码已修改');
+      ToastService.showSuccess(context, l10n?.passwordChanged ?? '密码已修改');
     } else {
-      ToastService.showError(context, '密码修改失败');
+      ToastService.showError(context, l10n?.passwordChangeFailed ?? '密码修改失败');
     }
   }
 
   @override
   Widget build(BuildContext context) {
+    final l10n = AppLocalizations.of(context);
     return ListView(
       padding: EdgeInsets.zero,
       children: [
@@ -95,7 +98,7 @@ class _PasswordPanelState extends ConsumerState<PasswordPanel> {
             crossAxisAlignment: CrossAxisAlignment.stretch,
             children: [
               Text(
-                '密码修改',
+                l10n?.password ?? '密码修改',
                 style: TextStyle(
                   color: AppTheme.textPrimary,
                   fontSize: 16,
@@ -105,20 +108,20 @@ class _PasswordPanelState extends ConsumerState<PasswordPanel> {
               const Divider(),
               _field(
                 controller: _oldCtrl,
-                label: '原密码',
-                hint: '请输入当前密码',
+                label: l10n?.oldPassword ?? '原密码',
+                hint: l10n?.enterCurrentPassword ?? '请输入当前密码',
               ),
               const SizedBox(height: 16),
               _field(
                 controller: _newCtrl,
-                label: '新密码',
-                hint: '至少6位字符',
+                label: l10n?.newPassword ?? '新密码',
+                hint: l10n?.passwordMinLength ?? '至少6位字符',
               ),
               const SizedBox(height: 16),
               _field(
                 controller: _confirmCtrl,
-                label: '确认新密码',
-                hint: '再次输入新密码',
+                label: l10n?.confirmNewPassword ?? '确认新密码',
+                hint: l10n?.enterNewPassword ?? '再次输入新密码',
               ),
               if (_error != null) ...[
                 const SizedBox(height: 12),
@@ -140,7 +143,7 @@ class _PasswordPanelState extends ConsumerState<PasswordPanel> {
                             _confirmCtrl.clear();
                             setState(() => _error = null);
                           },
-                    child: const Text('重置'),
+                    child: Text(l10n?.reset ?? '重置'),
                   ),
                   const SizedBox(width: 12),
                   ElevatedButton.icon(
@@ -155,7 +158,7 @@ class _PasswordPanelState extends ConsumerState<PasswordPanel> {
                             ),
                           )
                         : const Icon(Icons.check, size: 18),
-                    label: const Text('确认'),
+                    label: Text(l10n?.confirm ?? '确认'),
                   ),
                 ],
               ),
@@ -166,7 +169,7 @@ class _PasswordPanelState extends ConsumerState<PasswordPanel> {
         Padding(
           padding: const EdgeInsets.symmetric(horizontal: 4),
           child: Text(
-            '默认密码为 123456',
+            l10n?.defaultPassword ?? '默认密码为 123456',
             style: TextStyle(color: AppTheme.textSecondary, fontSize: 12),
           ),
         ),