feat(backend): 生产总天数返回自然天+工作日两个口径

- ProductResponse 加 production_days(自然天)/production_days_workdays(工作日)
- get_all_products 计算：自然天自创建至今，工作日用 working_duration_hours 排除周末/节假日
- FlowDevice 加 total_days/total_workdays(设备生产总天数，自最早介入至今)

backend/app/services/product_service.py

@@ -569,6 +569,27 @@ async def get_all_products(
             start_bj = to_beijing(start)  # 🚀 naive 按 UTC 转北京时间（修复多算8小时）
             active_duration_map[row[0]] = working_duration_hours(start_bj, now, holidays)
 
+    # 🔧 生产总天数（自然天 + 工作日）：自创建至今
+    import math
+    from app.core.time_utils import to_beijing as _tb, working_duration_hours as _wdh
+    from app.models.holiday import Holiday as _Holiday
+    hres2 = await db.execute(select(_Holiday.day))
+    holidays2 = {r[0] for r in hres2}
+    now2 = get_beijing_time()
+
+    def _prod_days(created_at):
+        created = _tb(created_at)
+        if not created:
+            return 1, 1
+        natural = max(1, math.ceil((now2 - created).total_seconds() / 86400))
+        work_hours = _wdh(created, now2, holidays2)
+        workdays = max(1, math.ceil(work_hours / 24))
+        return natural, workdays
+
+    production_days_map: dict = {}
+    for _p in products:
+        production_days_map[_p.id] = _prod_days(_p.created_at)
+
     return [
         ProductResponse(
             id=p.id,
@@ -604,6 +625,8 @@ async def get_all_products(
                 if latest_record_map.get(p.id, (None, None, False, None))[3] else None
             ),
             active_duration_hours=active_duration_map.get(p.id),
+            production_days=production_days_map.get(p.id, (1, 1))[0],
+            production_days_workdays=production_days_map.get(p.id, (1, 1))[1],
         )
         for p in products
     ]