feat(backend): 产品列表返回当前人滞留时长 active_duration_hours

- ProductResponse 增加 active_duration_hours(小时) 字段
- get_all_products 批量计算每个产品活跃任务(WIP/PENDING)最早接手时间到现在的时长
- 复用 get_people_workload 相同的北京时间口径，前端无需额外请求

backend/app/services/product_service.py

@@ -541,6 +541,34 @@ async def get_all_products(
             has_img = bool(row[3] and row[3] != "[]" and row[3] != "null")
             latest_record_map[row[0]] = (row[1], row[2], has_img, row[4])
 
+    # 🔧 当前人滞留时长：每个产品活跃任务(WIP/PENDING)最早接手时间 → 小时
+    active_duration_map: dict[uuid.UUID, float] = {}
+    if product_ids:
+        from sqlalchemy import func as sa_func
+        from app.core.time_utils import get_beijing_time, BEIJING_TZ
+        start_stmt = (
+            select(
+                Task.product_id,
+                sa_func.min(sa_func.coalesce(Task.received_at, Task.created_at)),
+            )
+            .where(
+                Task.product_id.in_(product_ids),
+                Task.status.in_(["WIP", "PENDING"]),
+            )
+            .group_by(Task.product_id)
+        )
+        start_result = await db.execute(start_stmt)
+        now = get_beijing_time()
+        for row in start_result:
+            start = row[1]
+            if start is None:
+                continue
+            if start.tzinfo is None:
+                start = start.replace(tzinfo=BEIJING_TZ)
+            else:
+                start = start.astimezone(BEIJING_TZ)
+            active_duration_map[row[0]] = round((now - start).total_seconds() / 3600, 1)
+
     return [
         ProductResponse(
             id=p.id,
@@ -575,6 +603,7 @@ async def get_all_products(
                 merged_name_map.get(latest_record_map.get(p.id, (None, None, False, None))[3])
                 if latest_record_map.get(p.id, (None, None, False, None))[3] else None
             ),
+            active_duration_hours=active_duration_map.get(p.id),
         )
         for p in products
     ]