feat(client): 商品详情加价格历史卡（接 /products/:id/price-history）

repo.getPriceHistory → 详情异步加载，新增价格历史卡：date + 进价，按相邻点
算涨跌（绿涨/红跌箭头）。至此商品详情 100% 对齐原型富数据版
（KPI + 各仓库分布 + 价格历史 + 近期流水）。golden 三主题已含该卡。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TSKEiHsvauyxYUW2itzUXX

client/lib/repositories/product_repository.dart

@@ -87,6 +87,27 @@ class ProductRepository {
     }
   }
 
+  /// 进价历史点（date/price），按日期倒序。失败抛 AppException。
+  Future<List<({String date, double price})>> getPriceHistory(int id) async {
+    try {
+      final resp = await _client.get('/products/$id/price-history');
+      final data = (resp.data as Map<String, dynamic>)['data'] as List? ?? [];
+      return data.map((e) {
+        final m = e as Map<String, dynamic>;
+        final d = (m['date'] as String? ?? '');
+        return (
+          date: d.length >= 10 ? d.substring(0, 10) : d,
+          price: (m['price'] as num).toDouble(),
+        );
+      }).toList();
+    } on DioException catch (e) {
+      throw AppException(
+        e.response?.data?['error'] as String? ?? '获取价格历史失败',
+        statusCode: e.response?.statusCode,
+      );
+    }
+  }
+
   Future<ProductImage> uploadImage(int productId, String? filePath,
       {Uint8List? bytes, String? fileName}) async {
     try {

client/lib/screens/products/product_detail_screen.dart

@@ -38,9 +38,10 @@ class _ProductDetailScreenState extends ConsumerState<ProductDetailScreen> {
   bool _savingDesc = false;
   bool _descChanged = false;
 
-  // 富数据（库存聚合 + 流水），随详情异步加载，失败不阻塞主数据。
+  // 富数据（库存聚合 + 流水 + 价格历史），随详情异步加载，失败不阻塞主数据。
   List<Inventory> _invRows = [];
   List<InventoryLog> _logs = [];
+  List<({String date, double price})> _prices = [];
 
   late TextEditingController _descCtrl;
 
@@ -82,10 +83,14 @@ class _ProductDetailScreenState extends ConsumerState<ProductDetailScreen> {
           await repo.listInventory(productId: widget.productId, pageSize: 1000);
       final logs =
           await repo.listLogs(productId: widget.productId, pageSize: 100);
+      final prices = await ref
+          .read(productRepositoryProvider)
+          .getPriceHistory(widget.productId);
       if (mounted) {
         setState(() {
           _invRows = inv.data;
           _logs = logs.data;
+          _prices = prices;
         });
       }
     } catch (_) {
@@ -311,6 +316,10 @@ class _ProductDetailScreenState extends ConsumerState<ProductDetailScreen> {
                   const SizedBox(height: 20),
                   _buildWarehouseDist(p),
                 ],
+                if (_prices.isNotEmpty) ...[
+                  const SizedBox(height: 20),
+                  _buildPriceHistory(),
+                ],
                 if (_logs.isNotEmpty) ...[
                   const SizedBox(height: 20),
                   _buildRecentLogs(),
@@ -452,6 +461,52 @@ class _ProductDetailScreenState extends ConsumerState<ProductDetailScreen> {
     );
   }
 
+  Widget _buildPriceHistory() {
+    return _statCard(
+      title: '价格历史',
+      hint: Text('进价变更',
+          style: TextStyle(fontSize: AppDims.fsXs, color: context.tokens.muted)),
+      body: Column(
+        children: _prices.asMap().entries.map((e) {
+          final i = e.key;
+          final p = e.value;
+          // _prices 倒序（新→旧）：i+1 是更早一笔，据此算涨跌。
+          final prev = i + 1 < _prices.length ? _prices[i + 1].price : null;
+          final up = prev != null && p.price > prev;
+          final down = prev != null && p.price < prev;
+          final color = up
+              ? context.tokens.success
+              : down
+                  ? context.tokens.danger
+                  : context.tokens.heading;
+          return Padding(
+            padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 9),
+            child: Row(
+              children: [
+                SizedBox(
+                  width: 96,
+                  child: Text(p.date,
+                      style: TextStyle(
+                          fontFamily: 'monospace',
+                          fontSize: AppDims.fsSm,
+                          color: context.tokens.muted)),
+                ),
+                if (up || down)
+                  Icon(up ? Icons.arrow_drop_up : Icons.arrow_drop_down,
+                      size: 18, color: color),
+                Text('¥${p.price.toStringAsFixed(2)}',
+                    style: TextStyle(
+                        fontFamily: 'monospace',
+                        fontWeight: FontWeight.w700,
+                        color: color)),
+              ],
+            ),
+          );
+        }).toList(),
+      ),
+    );
+  }
+
   Widget _buildRecentLogs() {
     return _statCard(
       title: '近期流水',

client/test/golden/product_detail_golden_test.dart

@@ -25,6 +25,14 @@ class _FakeProductRepo implements ProductRepository {
         series: '飞天', spec: '500ml×6', brand: '茅台',
         purchasePrice: 2680, categoryName: '酱香');
   @override
+  Future<List<({String date, double price})>> getPriceHistory(int id) async =>
+      const [
+        (date: '2026-06-12', price: 2680),
+        (date: '2026-04-20', price: 2620),
+        (date: '2026-02-08', price: 2700),
+        (date: '2025-11-15', price: 2580),
+      ];
+  @override
   dynamic noSuchMethod(Invocation invocation) =>
       super.noSuchMethod(invocation);
 }