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/announcements.py

@@ -1,11 +1,12 @@
 from datetime import datetime
-from typing import Optional
-from fastapi import APIRouter, Depends, Query, HTTPException
+
+from fastapi import APIRouter, Depends, HTTPException, Query
+from sqlalchemy import func, select
 from sqlalchemy.ext.asyncio import AsyncSession
-from sqlalchemy import select, func
+
 from app.api.deps import get_db
 from app.models.announcement import Announcement
-from app.models.schemas import AnnouncementResponse, AnnouncementListResponse
+from app.models.schemas import AnnouncementListResponse, AnnouncementResponse
 
 router = APIRouter()
 
@@ -14,11 +15,11 @@ router = APIRouter()
 async def list_announcements(
     page: int = Query(1, ge=1),
     page_size: int = Query(20, ge=1, le=100),
-    source_code: Optional[str] = None,
-    keyword: Optional[str] = None,
-    start_date: Optional[str] = None,
-    end_date: Optional[str] = None,
-    crawl_mode: Optional[str] = None,
+    source_code: str | None = None,
+    keyword: str | None = None,
+    start_date: str | None = None,
+    end_date: str | None = None,
+    crawl_mode: str | None = None,
     db: AsyncSession = Depends(get_db),
 ):
     conditions = []
@@ -91,12 +92,12 @@ async def get_stats(db: AsyncSession = Depends(get_db)):
         ).select_from(Announcement)
     )
     new_count = await db.execute(
-        select(func.count()).where(Announcement.is_new == True)
+        select(func.count()).where(Announcement.is_new == True)  # noqa: E712
         .select_from(Announcement)
     )
     unsent = await db.execute(
         select(func.count()).where(
-            Announcement.is_sent == False, Announcement.is_new == True
+            Announcement.is_sent == False, Announcement.is_new == True  # noqa: E712
         ).select_from(Announcement)
     )
     return {