feat(job): D1 Job 阶段上报（v3 §23）+ 列表/取消端点

- ResearchService.run_backtest/run_factor_test 支持 on_stage 回调（data_loading →
  factor_calculation/backtesting → analysis）；job_executor 经独立短会话把 stage 写库
  （子进程模式同样走 DB），收尾回读最后阶段避免覆盖
- /api/jobs：GET 列表（kind/limit）、POST /{id}/cancel（queued/running → CANCELLED +
  终止子进程 terminate_active；父进程兜底已跳过 CANCELLED）
- SSE /jobs/{id}/events 现会携带 stage
- tests/test_job_stages.py：成功 job 终态 stage=analysis；executor 取消 queued/幂等/
  已完成不可取消；API 列表+终态不可取消+404；全量 pytest 通过

backend/app/api/jobs.py

@@ -13,12 +13,13 @@ from __future__ import annotations
 import asyncio
 import json
 from datetime import datetime
+from typing import Annotated
 
-from fastapi import APIRouter, BackgroundTasks, HTTPException
+from fastapi import APIRouter, BackgroundTasks, HTTPException, Query
 from fastapi.responses import StreamingResponse
 
 from app.api.deps import DbSession, JobRepoDep
-from app.application.services.job_executor import new_id, run_job_background
+from app.application.services.job_executor import new_id, run_job_background, terminate_active
 from app.domain.entities.research import (
     BacktestResult,
     FactorTestReport,
@@ -69,6 +70,30 @@ def create_job(
     return {"job_id": job.id, "status": job.status}
 
 
+@router.get("", summary="Job 列表")
+def list_jobs(
+    job_repo: JobRepoDep,
+    kind: Annotated[str | None, Query(description="按类型过滤（backtest/factor_test）")] = None,
+    limit: Annotated[int, Query(ge=1, le=200)] = 20,
+) -> list[dict]:
+    return [_job_view(j) for j in job_repo.list_recent(kind=kind, limit=limit)]
+
+
+@router.post("/{job_id}/cancel", summary="取消 Job（queued/running）")
+def cancel_job(job_id: str, session: DbSession, job_repo: JobRepoDep) -> dict:
+    job = job_repo.get(job_id)
+    if job is None:
+        raise HTTPException(status_code=404, detail=f"Job {job_id} 不存在")
+    if job.status not in (JobStatus.QUEUED, JobStatus.RUNNING):
+        return {"job_id": job_id, "status": job.status, "cancelled": False}
+    job.status = JobStatus.CANCELLED
+    job.stage = None
+    job_repo.update(job)
+    session.commit()
+    terminate_active(job_id)  # 终止研究子进程（若有）；父进程兜底已跳过 CANCELLED
+    return {"job_id": job_id, "status": JobStatus.CANCELLED, "cancelled": True}
+
+
 @router.get("/{job_id}", summary="查询 Job 状态与结果")
 def get_job(job_id: str, job_repo: JobRepoDep) -> dict:
     job = job_repo.get(job_id)