feat(models): 扩充 Task 和 Product 数据库模型

Task 模型新增:
- received_at: DateTime (操作员确认接收时间)
- completed_at: DateTime (任务完工转交时间)
- reject_reason: String(500) (驳回原因)
- is_rework: Boolean (是否为返工任务，默认 False)
- 状态常量: PENDING/WIP/COMPLETED/REJECTED/ARCHIVED
- 默认状态由 'pending' 升为大写 'PENDING'

Product 模型新增:
- current_location_id: String(64) (当前持有者ID 或 'virtual_warehouse')

backend/app/models/product.py

@@ -33,6 +33,11 @@ class Product(Base):
         UUID(as_uuid=True), ForeignKey("products.id"), nullable=True, comment="父产品ID",
     )
 
+    # ---- 当前位置追踪（逻辑外键→用户ID 或 'virtual_warehouse'） ----
+    current_location_id: Mapped[str | None] = mapped_column(
+        String(64), nullable=True, comment="当前持有者ID 或 'virtual_warehouse'(仓库)",
+    )
+
     status: Mapped[str] = mapped_column(
         String(50), nullable=False, default="pending", comment="产品状态",
     )

backend/app/models/task.py

@@ -1,4 +1,4 @@
-"""任务模型 — 支持无限嵌套"""
+"""任务模型 — 支持无限嵌套、任务裂变分支、返工闭环"""
 import uuid
 from datetime import datetime, timezone
 from sqlalchemy import String, DateTime, Boolean, ForeignKey
@@ -7,6 +7,13 @@ from sqlalchemy.orm import Mapped, mapped_column, relationship
 
 from app.models.base import Base
 
+# 任务状态常量
+TASK_STATUS_PENDING = "PENDING"       # 待接收
+TASK_STATUS_WIP = "WIP"               # 进行中
+TASK_STATUS_COMPLETED = "COMPLETED"   # 已完成
+TASK_STATUS_REJECTED = "REJECTED"     # 已驳回
+TASK_STATUS_ARCHIVED = "ARCHIVED"     # 已入库
+
 
 class Task(Base):
     __tablename__ = "tasks"
@@ -20,9 +27,9 @@ class Task(Base):
         UUID(as_uuid=True), ForeignKey("products.id"), nullable=False, comment="所属产品ID",
     )
 
-    # ---- 物理外键（自引用：无限嵌套父子任务） ----
+    # ---- 物理外键（自引用：无限嵌套父子任务 / 裂变分支） ----
     parent_task_id: Mapped[uuid.UUID | None] = mapped_column(
-        UUID(as_uuid=True), ForeignKey("tasks.id"), nullable=True, index=True, comment="父任务ID",
+        UUID(as_uuid=True), ForeignKey("tasks.id"), nullable=True, index=True, comment="父任务ID(用于任务裂变树)",
     )
 
     task_name: Mapped[str] = mapped_column(
@@ -35,16 +42,32 @@ class Task(Base):
     )
 
     status: Mapped[str] = mapped_column(
-        String(50), nullable=False, default="pending", comment="任务状态",
+        String(50), nullable=False, default=TASK_STATUS_PENDING,
+        comment="任务状态: PENDING(待接收) | WIP(进行中) | COMPLETED(已完成) | REJECTED(已驳回) | ARCHIVED(已入库)",
     )
 
     notify_parent_on_complete: Mapped[bool] = mapped_column(
         Boolean, default=False, comment="完成后是否通知父任务",
     )
 
+    # ---- 时间追踪 ----
     created_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True), default=lambda: datetime.now(timezone.utc), comment="创建时间",
     )
+    received_at: Mapped[datetime | None] = mapped_column(
+        DateTime(timezone=True), nullable=True, comment="操作员确认接收时间",
+    )
+    completed_at: Mapped[datetime | None] = mapped_column(
+        DateTime(timezone=True), nullable=True, comment="任务完工转交时间",
+    )
+
+    # ---- 驳回/返工 ----
+    reject_reason: Mapped[str | None] = mapped_column(
+        String(500), nullable=True, comment="驳回原因",
+    )
+    is_rework: Mapped[bool] = mapped_column(
+        Boolean, default=False, comment="是否为返工任务",
+    )
 
     # ---- 关系 ----
     product: Mapped["Product"] = relationship("Product", lazy="selectin")