fix: 留言板区分业务序列号与系统追溯码

语义修正:
  Product.serial_number  = 16位HEX系统追溯码(如000000000000000D)
  Product.external_serial = 业务产品序列号(如25022)

后端:
  - ProductMessageItem 新增 external_serial 字段
  - search_product_messages 关联查询 Product.external_serial
  - 关键词搜索也支持按 external_serial 匹配

前端显示:
  样品升降台V1J · 序列号: 25022          ← 醒目
  追溯码: 000000000000000D               ← 10px浅灰小字

backend/app/services/dashboard_service.py

@@ -38,7 +38,8 @@ class ProductMessageItem(BaseModel):
     id: str
     content: str
     operator_name: str            # 留言人中文姓名
-    product_sn: str            # 16位SN
+    product_sn: str               # 16位HEX系统追溯码
+    external_serial: str | None   # 业务产品序列号（如 25022）
     material_name: str            # 物料名称
     created_at: str               # ISO时间字符串
 
@@ -194,9 +195,9 @@ async def search_product_messages(
     from app.models.product import Product
     from app.core.time_utils import BEIJING_TZ
 
-    # 基础查询
+    # 基础查询 — 同时取出 16位追溯码 + 业务序列号
     stmt = (
-        select(ProductMessage, Product.serial_number, Product.material_name)
+        select(ProductMessage, Product.serial_number, Product.material_name, Product.external_serial)
         .join(Product, ProductMessage.product_id == Product.id)
     )
 
@@ -205,6 +206,7 @@ async def search_product_messages(
         kw = f"%{keyword.strip()}%"
         stmt = stmt.where(or_(
             Product.serial_number.ilike(kw),
+            Product.external_serial.ilike(kw),
             Product.material_name.ilike(kw),
             ProductMessage.operator_id.ilike(kw),
             ProductMessage.content.ilike(kw),
@@ -227,7 +229,7 @@ async def search_product_messages(
         name_map = get_display_names(raw_ids)
 
     items: list[ProductMessageItem] = []
-    for msg, sn, mat_name in rows:
+    for msg, sn, mat_name, ext_sn in rows:
         t = msg.created_at
         if t:
             if t.tzinfo is None:
@@ -243,6 +245,7 @@ async def search_product_messages(
             content=msg.content,
             operator_name=name_map.get(msg.operator_id, msg.operator_id),
             product_sn=sn or "",
+            external_serial=ext_sn or None,
             material_name=mat_name or "",
             created_at=time_str,
         ))

frontend/src/pages/admin/AdminDashboard.tsx

@@ -127,11 +127,15 @@ function MsgRow({ m }: { m: ProductMessageItem }) {
             <span className="shrink-0 text-xs text-gray-400">{t}</span>
           </div>
           <p className="mb-2 text-sm leading-relaxed text-gray-600">{m.content}</p>
-          <div className="flex items-center gap-1 text-xs text-gray-500">
+          <div className="flex flex-col gap-0.5">
             {m.material_name && (
-              <span className="font-medium text-gray-700">{m.material_name}</span>
+              <span className="text-xs">
+                <span className="font-semibold text-gray-700">{m.material_name}</span>
+                <span className="text-gray-400"> · 序列号: </span>
+                <span className="font-medium text-gray-600">{m.external_serial || "未录入"}</span>
+              </span>
             )}
-            <span className="font-mono text-gray-400">(SN: {m.product_sn})</span>
+            <span className="text-[10px] text-gray-300 font-mono">追溯码: {m.product_sn}</span>
           </div>
         </div>
       </div>

frontend/src/services/dashboardApi.ts

@@ -30,6 +30,7 @@ export interface ProductMessageItem {
   content: string;
   operator_name: string;
   product_sn: string;
+  external_serial: string | null;
   material_name: string;
   created_at: string;
 }