feat: dedup expected data by handover_no before export submit

- store.get_existing_handover_nos: query PG expected_record.handover_no

- inject dedup skip before submitting export in zto/yunda/anneng/shunxin

- shunxin reads RTS handover_no from waybill-list view (method 1)

- force-redownload switch threaded via task_spec -> dispatch -> impl

- schema: add idx_expected_handover index

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

inbound_verify/store.py

@@ -422,6 +422,25 @@ def ingest_task(site, kind):
     return total
 
 
+def get_existing_handover_nos(site):
+    """查该站点已落库的交接单号集合（expected_record.handover_no）。
+    供"提交导出任务前"去重：已落库的交接单号不再重复提交导出任务。
+    PG 不可用（cpolar 抖动等）时返回空集 + 告警，调用方按"未确认存在"处理
+    （继续提交导出，UPSERT 兜底，绝不因去重查询失败而漏数据）。"""
+    try:
+        with _connect(_load_pg_config()["dbname"]) as conn:
+            with conn.cursor() as cur:
+                cur.execute(
+                    "SELECT handover_no FROM expected_record "
+                    "WHERE site=%s AND handover_no IS NOT NULL AND handover_no <> ''",
+                    (site,),
+                )
+                return {str(r[0]).strip() for r in cur.fetchall()}
+    except Exception as e:
+        print(f">> [去重] 查询已落库交接单号失败（{site}），本次不去重: {e}")
+        return set()
+
+
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