fix(discount): 折扣模型纠正——三类折扣各归其位，不取 min

- 客户折扣(discount 模块 get_min_product_discount) → amount 售价
- 供应商折扣(supplychain 模块 calculate_sale_amounts) → cost 平台进货成本
- 分销商折扣不进本函数(分销场景单独用 calculate_sale_amounts 的 distribution_amount)
- 供应商 id 来源：product.providerid，空则查 product_supplier_mapping 首选供应商

之前"取 min 三类折扣"是错的：用户折扣不能采用供应商折扣，两者独立。

product_management/core.py

@@ -1389,12 +1389,16 @@ class ProductManager:
 
     async def calculate_product_cost(self, product_id=None, product_code=None,
                                       usage_data=None, user_org_id=None):
-        """计算消费费用：资源真实定价 × 产品级折扣。
+        """计算消费费用：资源真实定价 + 客户折扣(售价) + 供应商折扣(成本)。
 
-        折扣精确到 product_id（discount_detail.productid），三类折扣取最优惠：
-        - 客户折扣：get_min_product_discount(product_id, resellerid, customerid)
-        - 分销商折扣：get_min_distributor_discount(product_id, resellerid, distributorid)
-        - 供应商折扣：get_min_supplier_discount(product_id, resellerid, supplierid)
+        三类折扣各自独立、归属不同环节，不取 min：
+        - 客户折扣   discount 模块 get_min_product_discount → amount（客户应付售价）
+        - 供应商折扣 supplychain 模块 calculate_sale_amounts → cost（平台进货成本）
+        - 分销商折扣 分销场景单独用（calculate_sale_amounts 的 distribution_amount），
+          不进本函数。
+
+        返回：original_amount(资源真实定价)、amount(售价=原价×客户折扣)、
+              cost(成本=原价×供应商折扣)、discount(客户折扣率)
         """
         iface, product, err = await self._get_product_interface(
             product_id, product_code)
@@ -1423,51 +1427,59 @@ class ProductManager:
         original_amount = float(result.get('original_amount',
                                            result.get('amount', 0) or 0))
 
-        # 2. 产品级折扣：精确到 product_id，取最优惠（min）
         env = ServerEnv()
         resellerid = product.get('org_id') or '0'
         pid = product.get('id') or ''
-        final_discount = 1.0
 
-        # 2a. 客户折扣（customerid 精确 + '*'/NULL 通配）
+        # 2. 客户折扣（discount 模块，售价侧）→ amount
+        discount = 1.0
         if user_org_id:
             try:
                 d = await env.get_min_product_discount(pid, resellerid, user_org_id)
                 if d not in (None, '', 0):
-                    final_discount = min(final_discount, float(d))
+                    discount = float(d)
             except Exception:
                 pass
+        amount = original_amount * discount
 
-        # 2b. 分销商折扣（客户归属的分销商，discount_customer_bind）
+        # 3. 供应商折扣（supplychain 模块，成本侧）→ cost
+        #    供应商折扣是平台进货折扣，与客户折扣独立，不取 min。
+        cost = original_amount
         try:
-            dbname = self._get_dbname()
-            async with DBPools().sqlorContext(dbname) as sor:
-                binds = await sor.R('discount_customer_bind',
-                                    {'customerid': user_org_id})
-                if binds:
-                    distributorid = getattr(binds[0], 'resellerid', '') or ''
-                    if distributorid:
-                        d = await env.get_min_distributor_discount(
-                            pid, resellerid, distributorid)
-                        if d not in (None, '', 0):
-                            final_discount = min(final_discount, float(d))
+            supplier_id = product.get('providerid') or ''
+            if not supplier_id:
+                # 从 supplychain 的产品→供应商映射查首选供应商
+                dbname = self._get_dbname()
+                async with DBPools().sqlorContext(dbname) as sor:
+                    maps = await sor.R('product_supplier_mapping',
+                                       {'product_id': pid})
+                    if maps:
+                        pref = [m for m in maps
+                                if str(getattr(m, 'is_preferred', '')) == '1'] or maps
+                        supplier_id = (getattr(pref[0], 'external_supplier_id', '')
+                                       or getattr(pref[0], 'supplier_org_id', '')
+                                       or '')
+            if supplier_id:
+                sc = await env.calculate_sale_amounts(None, {
+                    'resellerid': resellerid,
+                    'supplier_id': supplier_id,
+                    'productid': pid,
+                    'prodtypeid': product.get('category_id') or '',
+                    'quantity': 1,
+                    'unit_price': original_amount,
+                })
+                if sc:
+                    sc_data = json.loads(sc) if isinstance(sc, str) else sc
+                    sc_data = sc_data.get('data', {}) if isinstance(sc_data, dict) else {}
+                    supply_discount = float(sc_data.get('supply_discount', 1.0) or 1.0)
+                    cost = original_amount * supply_discount
         except Exception:
-            pass
+            cost = original_amount
 
-        # 2c. 供应商折扣（product.providerid）
-        supplierid = product.get('providerid') or ''
-        if supplierid:
-            try:
-                d = await env.get_min_supplier_discount(pid, resellerid, supplierid)
-                if d not in (None, '', 0):
-                    final_discount = min(final_discount, float(d))
-            except Exception:
-                pass
-
-        amount = original_amount * final_discount
         result['amount'] = round(amount, 6)
         result['original_amount'] = round(original_amount, 6)
-        result['discount'] = final_discount
+        result['cost'] = round(cost, 6)
+        result['discount'] = discount
         return result
 
     async def llm_id_to_product_id(self, llm_id):