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/crawler/dahuagov_spider.py

@@ -1,7 +1,9 @@
 import asyncio
 import random
 from datetime import datetime
+
 import httpx
+
 from app.config import settings
 from app.crawler.base import BaseSpider, CrawlResult, PipelineConfig
 from app.crawler.parsers import parse_dahuagov_html