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/models/announcement.py

@@ -1,6 +1,7 @@
 import hashlib
-from datetime import datetime, date
-from sqlalchemy import String, Boolean, DateTime, Integer, Text, func
+from datetime import datetime
+
+from sqlalchemy import Boolean, DateTime, Integer, String, Text, func
 from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column
 
 
@@ -25,7 +26,7 @@ class Announcement(Base):
     is_sent: Mapped[bool] = mapped_column(Boolean, default=False)
     keyword_matched: Mapped[bool] = mapped_column(Boolean, default=False)
     created_at: Mapped[datetime] = mapped_column(DateTime, server_default=func.now())
-    updated_at: Mapped[datetime] = mapped_column(DateTime, server_default=func.now(), onupdate=func.now())
+    updated_at: Mapped[datetime] = mapped_column(DateTime, server_default=func.now(), onupdate=func.now())  # noqa: E501
 
     @staticmethod
     def generate_hash(title: str, publish_date: str, purchase_name: str,
@@ -36,5 +37,6 @@ class Announcement(Base):
     @staticmethod
     def source_map() -> dict:
         import json
+
         from app.config import settings
         return json.loads(settings.announcement_sources)