chore: ruff 代码检查与修复

130 issues auto-fixed (import ordering, UP045/UP006 type annotations),
33 issues manually fixed (E712/E501/E402/E722 + N818 rename + per-file
wechat ignore for N8xx naming conventions). All 33 tests pass.

app/api/scheduler.py

@@ -1,6 +1,7 @@
 from fastapi import APIRouter
-from app.scheduler.jobs import scheduler
+
 from app.models.schemas import JobResponse
+from app.scheduler.jobs import scheduler
 
 router = APIRouter(prefix="/scheduler", tags=["scheduler"])