feat: 日报事件多新闻源入库(news_event.sources 列)

- ExtractedEvent 增加 sources 字段(主源居首去重,旧产物兜底 [source_id])
- extract_event(_async) 增加 sources 参数;run_event_extraction 读取
  deduped uniques 的 sources 透传
- reporter _load_events_from_dir 读取 sources → EventRow.sources
- news_event 建表加 sources TEXT 列;init_schema 幂等迁移旧表(捕获
  Duplicate column);save_report INSERT 写 JSON 多源
- 新增测试:ExtractedEvent/EventRow.sources 兜底与保序、_load_events_from_dir 多源

tests/test_report_db.py

@@ -20,9 +20,16 @@ class TestEventRow:
         ev = EventRow(
             section="intl", rank=2, importance=4, event_type="地缘政治",
             title="t", summary="s", sentiment="negative", source="ForexLive",
+            sources=["ForexLive", "新浪财经"],
             url="https://x.com/1",
         )
         assert ev.sentiment == "negative"
+        assert ev.sources == ["ForexLive", "新浪财经"]
+
+    def test_sources_optional(self) -> None:
+        """sources 为可选项(旧数据无多源记录)。"""
+        ev = EventRow(section="news", rank=1, title="t")
+        assert ev.sources is None
 
     def test_missing_title_raises(self) -> None:
         with pytest.raises(ValidationError):