feat: make core pages local-first offline

frontend/lib/features/stats/stats_page.dart

@@ -1,4 +1,5 @@
 import 'dart:math' as math;
+import 'dart:async';
 import 'package:miaoji_zhang/shared/services/shanghai_time.dart';
 
 import 'package:flutter/material.dart';
@@ -8,6 +9,7 @@ import 'package:miaoji_zhang/shared/services/current_ledger_store.dart';
 import 'package:miaoji_zhang/shared/theme/app_theme.dart';
 import 'package:miaoji_zhang/shared/widgets/app_controls.dart';
 import 'package:miaoji_zhang/shared/widgets/async_error_view.dart';
+import 'package:miaoji_zhang/shared/widgets/backend_status_icon.dart';
 import 'package:miaoji_zhang/shared/widgets/category_icon.dart';
 
 class StatsPage extends StatefulWidget {
@@ -23,12 +25,13 @@ class _StatsPageState extends State<StatsPage> {
   PeriodStats? _stats;
   String? _error;
   bool _loading = true;
+  int _loadRevision = 0;
 
   @override
   void initState() {
     super.initState();
     CurrentLedgerStore.instance.addListener(_load);
-    _load();
+    unawaited(_load());
   }
 
   @override
@@ -38,6 +41,7 @@ class _StatsPageState extends State<StatsPage> {
   }
 
   Future<void> _load() async {
+    final revision = ++_loadRevision;
     if (mounted) {
       setState(() {
         _loading = true;
@@ -45,12 +49,25 @@ class _StatsPageState extends State<StatsPage> {
       });
     }
     try {
-      final stats = await TxApi.periodStats(_period, _anchor);
-      if (mounted) setState(() => _stats = stats);
+      final local = TxApi.periodStatsLocal(_period, _anchor);
+      if (mounted && revision == _loadRevision) {
+        setState(() => _stats = local);
+      }
     } catch (error) {
-      if (mounted) setState(() => _error = apiErrorMessage(error));
+      if (mounted && revision == _loadRevision) {
+        setState(() => _error = apiErrorMessage(error));
+      }
+    }
+    try {
+      final remote = await TxApi.periodStatsRemote(_period, _anchor);
+      if (mounted && revision == _loadRevision) {
+        setState(() => _stats = remote);
+      }
+    } catch (_) {
     } finally {
-      if (mounted) setState(() => _loading = false);
+      if (mounted && revision == _loadRevision) {
+        setState(() => _loading = false);
+      }
     }
   }
 
@@ -93,7 +110,10 @@ class _StatsPageState extends State<StatsPage> {
   Widget build(BuildContext context) {
     final stats = _stats;
     return Scaffold(
-      appBar: AppBar(title: Text('统计')),
+      appBar: AppBar(
+        title: Text('统计'),
+        actions: [BackendStatusIcon(onRetry: _load)],
+      ),
       body: Column(
         children: [
           Padding(
@@ -105,7 +125,7 @@ class _StatsPageState extends State<StatsPage> {
                 JzOption(value: 'month', label: '月'),
                 JzOption(value: 'year', label: '年'),
               ],
-              onChanged: _loading ? null : _selectPeriod,
+              onChanged: _selectPeriod,
             ),
           ),
           Expanded(
@@ -171,7 +191,7 @@ class _StatsPageState extends State<StatsPage> {
       children: [
         IconButton(
           tooltip: '上一个周期',
-          onPressed: _loading ? null : () => _shift(-1),
+          onPressed: () => _shift(-1),
           icon: Icon(Icons.chevron_left_rounded),
         ),
         SizedBox(
@@ -184,9 +204,7 @@ class _StatsPageState extends State<StatsPage> {
         ),
         IconButton(
           tooltip: '下一个周期',
-          onPressed: _loading || _isAfterCurrentPeriod(nextAnchor)
-              ? null
-              : () => _shift(1),
+          onPressed: _isAfterCurrentPeriod(nextAnchor) ? null : () => _shift(1),
           icon: Icon(Icons.chevron_right_rounded),
         ),
       ],