refactor(backend): jobs 读端点走 JobRepo 而非路由内裸 ORM

GET /jobs/{id} 原在路由里直接 select(Job) 裸 ORM 查询；改为经 get_job_repo
注入 JobRepo 调 .get(job_id)，与项目其它端点的 Repository 分层一致，
测试可经 dependency_overrides 注 fake。行为不变（同一 session 同一查询）。

apps/api/ww_api/routers/jobs.py

@@ -6,13 +6,11 @@ import uuid
 from typing import Annotated
 
 from fastapi import APIRouter, Depends
-from sqlalchemy import select
-from sqlalchemy.ext.asyncio import AsyncSession
-from ww_db import get_session
-from ww_db.models import Job
+from ww_core.domain import JobRepo
 from ww_shared import AppError, ErrorCode, ErrorEnvelope
 
 from ww_api.schemas.jobs import JobResponse
+from ww_api.services.project_deps import get_job_repo
 
 router = APIRouter(prefix="/jobs", tags=["jobs"])
 
@@ -23,9 +21,9 @@ router = APIRouter(prefix="/jobs", tags=["jobs"])
 )
 async def get_job(
     job_id: uuid.UUID,
-    session: Annotated[AsyncSession, Depends(get_session)],
+    job_repo: Annotated[JobRepo, Depends(get_job_repo)],
 ) -> JobResponse:
-    job = (await session.execute(select(Job).where(Job.id == job_id))).scalar_one_or_none()
+    job = await job_repo.get(job_id)
     if job is None:
         raise AppError(ErrorCode.NOT_FOUND, f"job {job_id} not found")
     return JobResponse(