fix(golden): 冻结应用时钟消除时间依赖非确定性(product_detail/license/inventory_check)

golden 失败根因:商品详情屏用实时 DateTime.now() 算「近30天出库」,随真实时间推移
6月流水掉出30天窗口→渲染变化→对不上。license/inventory_check 同理(剩余天数/盘点日期)。
修复:
- product_detail_screen: DateTime.now() → appNow()(可注入时钟)
- golden_harness: 所有 golden 渲染前冻结 appClock=2026-07-01 + tearDown 复位(ds-flow 钉死动态值)
- 重录 license_mobile / m_inventory_check 6 张 golden;product_detail 冻结后自动匹配无需改图
本地 flutter test test/golden/ 全 120 通过。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01P9G7E3wmAYL9KeYCVZVsqu

client/lib/screens/products/product_detail_screen.dart

@@ -1,5 +1,6 @@
 import 'package:lucide_icons_flutter/lucide_icons.dart';
 import '../../core/utils/dialog_util.dart';
+import '../../core/utils/clock.dart';
 import 'package:file_picker/file_picker.dart';
 import 'package:image_picker/image_picker.dart';
 import 'package:flutter/foundation.dart';
@@ -395,7 +396,7 @@ class _ProductDetailScreenState extends ConsumerState<ProductDetailScreen> {
     final currentStock = _invRows.fold<num>(0, (s, i) => s + i.quantity);
     final cost = p.purchasePrice ?? 0;
     final stockValue = currentStock * cost;
-    final now = DateTime.now();
+    final now = appNow();
     final out30 = _logs.where((l) {
       if (l.direction != 'out') return false;
       final d = DateTime.tryParse(l.createdAt ?? '');

client/test/support/golden_harness.dart

@@ -3,6 +3,7 @@ import 'package:flutter/services.dart' show rootBundle, FontLoader;
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:jiu_client/core/theme/themes.dart';
+import 'package:jiu_client/core/utils/clock.dart';
 
 // 加载真实中文字体（消除 golden 豆腐块），使 golden 能与原型截图做保真 diff。
 // 原型截图侧同样注入 Noto Sans SC（见 tools/fidelity.mjs），两边字体一致。
@@ -67,6 +68,11 @@ Future<void> pumpGolden(
   double dpr = 2.0,
 }) async {
   await ensureGoldenFonts();
+  // 冻结应用时钟：凡走 appNow() 的展示计算（如商品详情「近30天出库」）不再依赖真实时间，
+  // 保证 golden 确定性（ds-flow：golden 钉死一切动态值）。选 2026-07-01，使 fake 6 月流水
+  // 稳定落在「近30天」窗口内。tearDown 复位，不影响其它测试。
+  appClock = () => DateTime(2026, 7, 1, 12, 0);
+  addTearDown(() => appClock = () => DateTime.now());
   tester.view.physicalSize = Size(logical.width * dpr, logical.height * dpr);
   tester.view.devicePixelRatio = dpr;
   addTearDown(tester.view.resetPhysicalSize);