feat(programs): Excel 模板下载 + .xlsx 解析导入

- 新增 excel 4.0.6 / path_provider 2.1.5 依赖
- ExcelTemplateService：生成 Programs + Steps 双表模板（保存到应用文档目录）
- ExcelImportService：解析 .xlsx 并写入数据库，跳过已存在 code、按 program_code 关联步骤
- programs_page 顶部新增「下载模板」按钮，导入按钮改用 Excel 解析
- 移除被取代的 program_import_service.dart
- AppLocalizations 新增 downloadTemplate 键
- 验证：flutter analyze 无新增 issue；flutter build apk --debug 通过

lib/features/programs/pages/programs_page.dart

@@ -5,11 +5,13 @@ import 'package:file_picker/file_picker.dart';
 import 'dart:io';
 import '../../../core/localization/app_localizations.dart';
 import '../../../core/theme/app_theme.dart';
+import '../../../shared/services/toast_service.dart';
 import '../../../shared/widgets/common_button.dart';
 import '../models/program.dart';
 import '../providers/programs_provider.dart';
 import '../widgets/program_form_dialog.dart';
-import '../services/program_import_service.dart';
+import '../services/excel_import_service.dart';
+import '../services/excel_template_service.dart';
 
 /// 程序管理页面
 class ProgramsPage extends ConsumerStatefulWidget {
@@ -64,6 +66,14 @@ class _ProgramsPageState extends ConsumerState<ProgramsPage> {
                     onPressed: () => _showAddDialog(context, ref),
                   ),
                   const SizedBox(width: 12),
+                  // 下载模板按钮
+                  CommonButton(
+                    text: l10n?.downloadTemplate ?? '下载模板',
+                    icon: Icons.file_download,
+                    type: ButtonType.secondary,
+                    onPressed: () => _downloadTemplate(context),
+                  ),
+                  const SizedBox(width: 12),
                   // 导入按钮
                   CommonButton(
                     text: l10n?.importProgram ?? '导入',
@@ -407,7 +417,7 @@ class _ProgramsPageState extends ConsumerState<ProgramsPage> {
       // 选择文件
       final result = await FilePicker.platform.pickFiles(
         type: FileType.custom,
-        allowedExtensions: ['json'],
+        allowedExtensions: ['xlsx'],
         allowMultiple: false,
       );
 
@@ -417,38 +427,39 @@ class _ProgramsPageState extends ConsumerState<ProgramsPage> {
 
       final file = result.files.first;
       if (file.path == null) {
-        ScaffoldMessenger.of(context).showSnackBar(
-          SnackBar(
-            content: Text('无法读取文件'),
-            backgroundColor: AppTheme.errorColor,
-          ),
-        );
+        if (!context.mounted) return;
+        ToastService.showError(context, '无法读取文件');
         return;
       }
 
-      // 读取文件内容
-      final jsonContent = await File(file.path!).readAsString();
-
-      // 导入程序
-      final importedCount = await ProgramImportService.instance.importFromJson(jsonContent);
+      // 解析并写入数据库
+      final importedCount =
+          await ExcelImportService.instance.importFromExcel(File(file.path!));
 
       // 刷新程序列表
       ref.read(programsProvider.notifier).loadPrograms();
 
-      // 显示结果
-      ScaffoldMessenger.of(context).showSnackBar(
-        SnackBar(
-          content: Text('成功导入 $importedCount 个程序'),
-          backgroundColor: importedCount > 0 ? AppTheme.successColor : AppTheme.warningColor,
-        ),
-      );
+      if (!context.mounted) return;
+      if (importedCount > 0) {
+        ToastService.showSuccess(context, '成功导入 $importedCount 个程序');
+      } else {
+        ToastService.showWarning(context, '未导入新程序（编号可能已存在）');
+      }
     } catch (e) {
-      ScaffoldMessenger.of(context).showSnackBar(
-        SnackBar(
-          content: Text('导入失败: ${e.toString()}'),
-          backgroundColor: AppTheme.errorColor,
-        ),
-      );
+      if (!context.mounted) return;
+      ToastService.showError(context, '导入失败: ${e.toString()}');
+    }
+  }
+
+  /// 下载 Excel 模板
+  Future<void> _downloadTemplate(BuildContext context) async {
+    try {
+      final file = await ExcelTemplateService.instance.generateTemplate();
+      if (!context.mounted) return;
+      ToastService.showSuccess(context, '模板已保存: ${file.path}');
+    } catch (e) {
+      if (!context.mounted) return;
+      ToastService.showError(context, '生成模板失败: ${e.toString()}');
     }
   }