feat: 最新公告点击时触发爬取并优化查询逻辑

- 点击时先爬取一次（60秒防重入），爬取期间发送提示
- 查询改为：广西政采网关键词匹配 + 大化县政府网全部，按时间倒序取6条

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/wechat/handler.py

@@ -13,6 +13,10 @@ logger = logging.getLogger(__name__)
 _last_crawl_time: float = 0.0
 _crawl_lock = asyncio.Lock()
 
+# 防重入：最新公告爬取，60秒内不重复执行
+_last_latest_time: float = 0.0
+_latest_lock = asyncio.Lock()
+
 
 class WeChatMessageHandler:
     def __init__(self):
@@ -237,14 +241,32 @@ class WeChatMessageHandler:
             await self.client.send_text("查询失败，请稍后再试", from_user)
 
     async def _handle_latest_announcements(self, from_user: str) -> str | None:
-        from app.api.deps import get_db
-        from sqlalchemy import select, desc
+        global _last_latest_time
+        from app.api.deps import get_db, get_crawl_service
+        from sqlalchemy import select, desc, or_
         from app.models.announcement import Announcement
 
         try:
+            # 防重入：60秒内只爬取一次
+            async with _latest_lock:
+                now = time.monotonic()
+                do_crawl = (now - _last_latest_time) >= 60
+                if do_crawl:
+                    _last_latest_time = now
+
+            if do_crawl:
+                await self.client.send_text("正在获取最新公告，请稍候...", from_user)
+                service = get_crawl_service()
+                await service.run_all()
+
+            # 查：广西政采网关键词匹配 + 大化县政府网全部
             async for db in get_db():
                 result = await db.execute(
                     select(Announcement)
+                    .where(or_(
+                        Announcement.keyword_matched == True,  # noqa: E712
+                        Announcement.source_code == "dahuagov",
+                    ))
                     .order_by(desc(Announcement.publish_date))
                     .limit(6)
                 )