feat(pl): add pl_plan.copy_seq_no for copy-to-group sequence

Persist a tenant-scoped fixed serial for driver-plan clipboard text;
include migration backfill by create_time.

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

docs/sql/shanxia2.0.sql

@@ -25732,6 +25732,7 @@ DROP TABLE IF EXISTS `pl_plan`;
 CREATE TABLE `pl_plan` (
   `id` varchar(64) NOT NULL COMMENT '主键ID',
   `plan_no` varchar(32) NOT NULL COMMENT '计划订单编号 SXDDHYYYYMMDD######',
+  `copy_seq_no` int(11) DEFAULT NULL COMMENT '复制发群序号（租户内固定流水，首次复制时分配）',
   `create_date` date NOT NULL COMMENT '创建日期',
   `plan_date` date DEFAULT NULL COMMENT '计划日期',
   `belongs_company` varchar(20) NOT NULL COMMENT '归属公司 shanxia-安庆山峡 yundong-安徽云栋',
@@ -25807,6 +25808,7 @@ CREATE TABLE `pl_plan` (
   PRIMARY KEY (`id`) USING BTREE,
   UNIQUE KEY `uk_plan_no` (`plan_no`) USING BTREE,
   KEY `idx_tenant` (`tenant_no`) USING BTREE,
+  KEY `idx_pl_plan_tenant_copy_seq` (`tenant_no`, `copy_seq_no`) USING BTREE,
   KEY `idx_plan_type` (`plan_type`) USING BTREE,
   KEY `idx_follow_status` (`follow_status`) USING BTREE,
   KEY `idx_plan_date` (`plan_date`) USING BTREE,