fix: support offline manual bookkeeping

frontend/test/offline_local_first_test.dart

@@ -5,6 +5,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:miaoji_zhang/shared/api/api_client.dart';
 import 'package:miaoji_zhang/shared/api/auth_api.dart';
+import 'package:miaoji_zhang/shared/services/local_database.dart';
 import 'package:miaoji_zhang/shared/widgets/backend_status_icon.dart';
 
 void main() {
@@ -79,6 +80,31 @@ void main() {
     expect(companion.toJson(), source);
   });
 
+  test('账号分类缓存为空时会补齐支出和收入兜底并允许本地记账', () {
+    final database = LocalDatabase.inMemoryForTesting(seedDefaults: false);
+    addTearDown(database.close);
+
+    database.ensureDefaultCategories();
+    final expense = database.categories('expense');
+    final income = database.categories('income');
+
+    expect(expense, hasLength(12));
+    expect(income, hasLength(7));
+    expect(expense.first['name'], '餐饮');
+    expect(income.first['name'], '工资');
+    expect(income.first['id'], 13);
+
+    final transaction = database.createTransaction({
+      'ledgerId': 1,
+      'categoryId': expense.first['id'],
+      'type': 'expense',
+      'amount': 18.5,
+      'occurredAt': DateTime.utc(2026, 8, 21).toIso8601String(),
+    });
+    expect(transaction['amount'], 18.5);
+    expect(transaction['categoryName'], '餐饮');
+  });
+
   test('七个页面保持本地首屏、后台刷新、竞态保护和统一离线入口', () {
     final contracts = <String, List<String>>{
       'lib/features/home/pages/home_page.dart': [
@@ -92,6 +118,7 @@ void main() {
         "categoriesLocal('expense')",
         "categoriesRemote('expense')",
         "categoriesRemote('income')",
+        'localFirst: true',
       ],
       'lib/features/stats/stats_page.dart': [
         'periodStatsLocal',
@@ -104,6 +131,7 @@ void main() {
       'lib/features/settings/category_manage_page.dart': [
         'categoriesLocal',
         'categoriesRemote',
+        'localFirst: true',
       ],
       'lib/features/settings/recycle_bin_page.dart': [
         'recycleBinLocal',