feat(flow): support dynamic countersign add-sign

db/upgrade/20260716_dynamic_add_sign.sql

@@ -0,0 +1,30 @@
+-- 动态会签加签：存量数据库一次性升级脚本
+
+ALTER TABLE `process_node_record_assign_user`
+  ADD COLUMN `node_record_id` bigint DEFAULT NULL COMMENT '本轮节点执行记录id' AFTER `local_data`,
+  ADD COLUMN `assignment_origin` varchar(20) NOT NULL DEFAULT 'ORIGINAL' COMMENT '分配来源 ORIGINAL/ADD_SIGN' AFTER `node_record_id`,
+  ADD COLUMN `initial_user_id` bigint DEFAULT NULL COMMENT '本份待办最初分配用户id' AFTER `assignment_origin`,
+  ADD COLUMN `add_sign_record_id` bigint DEFAULT NULL COMMENT '动态加签批次记录id' AFTER `initial_user_id`,
+  ADD UNIQUE KEY `uk_node_record_user` (`tenant_id`, `node_record_id`, `user_id`),
+  ADD KEY `idx_add_sign_record_id` (`add_sign_record_id`);
+
+CREATE TABLE `process_task_add_sign_record` (
+  `id` bigint NOT NULL COMMENT '主键id',
+  `del_flag` char(1) DEFAULT '0' COMMENT '删除标志',
+  `create_time` datetime DEFAULT NULL COMMENT '创建时间',
+  `update_time` datetime DEFAULT NULL COMMENT '更新时间',
+  `flow_id` varchar(255) NOT NULL COMMENT '流程id',
+  `process_instance_id` varchar(50) NOT NULL COMMENT '流程实例id',
+  `node_record_id` bigint NOT NULL COMMENT '本轮节点执行记录id',
+  `node_id` varchar(50) NOT NULL COMMENT '节点id',
+  `source_task_id` varchar(255) NOT NULL COMMENT '发起加签的任务id',
+  `added_by_user_id` bigint NOT NULL COMMENT '加签发起人id',
+  `reason` varchar(100) NOT NULL COMMENT '加签原因',
+  `target_user_ids` longtext NOT NULL COMMENT '本批次目标用户快照',
+  `participant_user_ids_before` longtext NOT NULL COMMENT '操作前参与人快照',
+  `participant_user_ids_after` longtext DEFAULT NULL COMMENT '操作后参与人快照',
+  `tenant_id` bigint NOT NULL DEFAULT '0' COMMENT '所属租户id',
+  PRIMARY KEY (`id`),
+  KEY `idx_add_sign_node_record` (`tenant_id`, `node_record_id`),
+  KEY `idx_add_sign_process_instance` (`tenant_id`, `process_instance_id`)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci ROW_FORMAT=DYNAMIC COMMENT='流程动态加签批次记录';