调整embedding策略

只处理2周内的新闻，利用索引、时间降序

cucyuqing/cmd/embedding.py

@@ -177,7 +177,14 @@ async def do_update():
     while True:
         async with get_cur() as cur:
             # 这里选择 embedding_updated_at is null 使用索引避免全表扫描
-            await cur.execute("SELECT id, title, content from risk_news where embedding_updated_at is null limit 1000")
+            await cur.execute("""
+                SELECT id, title, content
+                from risk_news
+                where embedding_updated_at is null
+                    and time > now() - interval '14 day'
+                order by time desc
+                limit 1000
+            """)
             docs = await cur.fetchall()
 
         # 循环出口