feat(pl): allocate copy_seq_no on first driver plan share-to-group

Add ensure-copy-seq API and miniprogram clipboard prefix so each plan
gets a tenant-scoped fixed serial on first copy; cover allocation with
unit tests and refresh the backend graph.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/app/api/pl/driver_plan.py

@@ -82,6 +82,28 @@ def get_driver_plan_detail(
     return success_response(page.model_dump(by_alias=True))
 
 
+@router.post("/{plan_id}/ensure-copy-seq")
+def ensure_driver_plan_copy_seq(
+    plan_id: str,
+    db: Session = Depends(get_db),
+    user: DbUserContext = Depends(get_db_current_user),
+):
+    tenant_no = get_tenant_no(db, user.to_tenant_user_dict())
+    personnel = _resolve_personnel_or_empty(db, user, tenant_no)
+    if not personnel:
+        raise HTTPException(status_code=404, detail="未关联驾押人员，无法查看")
+    seq, err = drv_svc.ensure_copy_seq_for_driver(
+        db,
+        tenant_no=tenant_no,
+        plan_id=plan_id,
+        personnel_id=personnel.id,
+    )
+    if err or seq is None:
+        raise HTTPException(status_code=404, detail=err or "计划不存在")
+    db.commit()
+    return success_response({"copySeqNo": seq})
+
+
 @router.post("/{plan_id}/feedback")
 def save_driver_plan_feedback(
     plan_id: str,