feat(task): 任务中心扫码接单(多端) —— 服务端任务状态机/端口/迁移

- Task 加 task_code/tags/display_priority/claimed_by/claimed_at/doing_at；新增 TaskClaim 流水表。
- TaskService 加 claimed/doing/completed 状态机(claim/start_doing/complete)，grab 并入 claim。
- TaskRepository 加 list_published/get_by_code/update/claim/set_doing + TaskClaimRepository；挂 Database。
- 端口：
  · opc  /tasks/grab-by-code、/tasks/{id}/doing、/tasks/{id}/complete
  · operator POST /tasks(auto task_code) + PATCH /tasks/:id
  · park  /park/api/tasks(大屏展示,含 scan_payload 二维码载荷)
  · training /api/tasks/claim-by-code、/api/tasks/my(小程序 C 端账号→OPC 身份 find-or-create 领单)
- 迁移 0008(tasks 加列 + task_claims)已应用+stamp；seed 补 task_code/tags/grab demo。
- tests/test_task_claim.py(自包含内存库, 状态机+流水+list_published), 直接 async 校验通过。

Co-Authored-By: Claude <noreply@anthropic.com>

tests/test_task_claim.py

@@ -0,0 +1,92 @@
+# -*- coding: utf-8 -*-
+"""任务中心·扫码接单：TaskService 状态机 + Repository 访问（自包含内存库）。"""
+from __future__ import annotations
+
+from contextlib import asynccontextmanager
+
+import pytest
+from fastapi import HTTPException
+from sqlalchemy.ext.asyncio import async_sessionmaker, create_async_engine
+
+from app.infrastructure.models import Base  # noqa: F401  (注册表到 Base)
+from app.infrastructure.repositories import Database
+from app.services.task_service import TaskService
+
+
+@asynccontextmanager
+async def _db():
+    engine = create_async_engine("sqlite+aiosqlite:///:memory:")
+    async with engine.begin() as conn:
+        await conn.run_sync(Base.metadata.create_all)
+    Session = async_sessionmaker(engine, expire_on_commit=False)
+    async with Session() as session:
+        yield Database(session=session)
+    await engine.dispose()
+
+
+def _grab_published(**kw):
+    return dict(
+        task_code="TK-004-GRAB", title="短视频剪辑", mode="grab",
+        status="published", category="技术开发", budget_min=1500, budget_max=3000,
+        display_priority=30, **kw,
+    )
+
+
+async def test_claim_marks_claimed_and_records_claim():
+    """published + grab → claimed（claimed_by/claimed_at），并写 task_claims 流水。"""
+    async with _db() as db:
+        t = await db.tasks.create(_grab_published())
+        actor = {"id": "u_opc_1", "username": "opc01", "nickname": "阿健"}
+        res = await TaskService(db).claim(t["task_code"], actor, source="scan")
+        assert res["status"] == "claimed"
+        assert res["claimed_by"] == "u_opc_1"
+        assert res["claimed_at"]
+        claims = await db.task_claims.list_by_task(t["id"])
+        assert claims and claims[0]["claim_source"] == "scan"
+
+
+async def test_claim_disallowed_non_grab_mode():
+    """bid 模式不可扫码接单。"""
+    async with _db() as db:
+        t = await db.tasks.create(_grab_published(title="UI", mode="bid"))
+        with pytest.raises(HTTPException):
+            await TaskService(db).claim(t["task_code"], {"id": "u1"}, "scan")
+
+
+async def test_claim_unknown_code_404():
+    async with _db() as db:
+        with pytest.raises(HTTPException):
+            await TaskService(db).claim("TK-NOT-EXIST", {"id": "u1"}, "scan")
+
+
+async def test_claim_already_claimed_rejected():
+    """已 claim 的任务再 claim 应报错。"""
+    async with _db() as db:
+        t = await db.tasks.create(_grab_published())
+        await TaskService(db).claim(t["task_code"], {"id": "u1"}, "scan")
+        with pytest.raises(HTTPException):
+            await TaskService(db).claim(t["task_code"], {"id": "u2"}, "scan")
+
+
+async def test_doing_then_complete():
+    """claimed → doing → completed。"""
+    async with _db() as db:
+        t = await db.tasks.create(_grab_published())
+        actor = {"id": "u_opc_1", "username": "opc01", "nickname": "阿健"}
+        await TaskService(db).claim(t["task_code"], actor, source="scan")
+        doing = await TaskService(db).start_doing(t["id"], actor)
+        assert doing["status"] == "doing" and doing["doing_at"]
+        done = await TaskService(db).complete(t["id"], actor)
+        assert done["status"] == "completed"
+
+
+async def test_list_published_returns_display_fields():
+    """大屏取数：list_published 返回新字段且按 display_priority 降序。"""
+    async with _db() as db:
+        await db.tasks.create(_grab_published(task_code="TK-LOW", display_priority=1))
+        await db.tasks.create(_grab_published(task_code="TK-HIGH", display_priority=99))
+        items = await db.tasks.list_published()
+        codes = [t["task_code"] for t in items]
+        assert "TK-LOW" in codes and "TK-HIGH" in codes
+        assert codes.index("TK-HIGH") < codes.index("TK-LOW")
+        assert all("task_code" in t and "claimed_by" in t for t in items)