feat(services): 核心业务逻辑 — 接收/返工/裂变/记录/标签打印

task_service:
- receive_task() — PENDING→WIP, 记录 received_at
- reject_task() — →REJECTED + 自动返工闭环
- transfer_task() — →COMPLETED + 多路裂变 + virtual_warehouse入库
- add_task_record() — 图文记录追加
- 全链路 selectinload(Task.records)
- 全部 now 改用 get_beijing_time()

product_service:
- create_product() — PG Sequence 自动生成16位HEX
- update_overall_status() — 宏观状态校验+更新
- 扫码返回完整 task_tree (含 records)
- order_no 自由文本→自动创建 ProductionOrder
- update_product() 支持 order_no 编辑

label_service:
- 480×360 工业级排版 (QR+名/规/单+底部通栏码)
- simhei.ttf 34px/28px + stroke_width 描边
- TSPL Socket 发送到打标机

backend/app/services/__init__.py

@@ -4,6 +4,7 @@ from app.services.product_service import (
     get_product,
     create_product,
     update_product,
+    update_overall_status,
     get_all_products,
 )
 from app.services.task_service import (
@@ -16,6 +17,7 @@ from app.services.task_service import (
     reject_task,
     transfer_task,
     create_subtask,
+    add_task_record,
     get_all_tasks,
 )
 
@@ -25,6 +27,7 @@ __all__ = [
     "get_product",
     "create_product",
     "update_product",
+    "update_overall_status",
     "get_all_products",
     # Task
     "get_task",
@@ -36,5 +39,6 @@ __all__ = [
     "reject_task",
     "transfer_task",
     "create_subtask",
+    "add_task_record",
     "get_all_tasks",
 ]