feat(oa): add return, resubmit, and multi-round approval progress

Align with DingTalk semantics: reject ends the instance, return keeps it for initiator edits, and revoke-and-resubmit creates a linked new instance. Progress timeline projects rounds via oa_instance_event.

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

docs/sql/patch_2026-07-15_oa_progress_return.sql

@@ -0,0 +1,34 @@
+-- OA 审批进度多轮 + 打回 + 撤销重提关联
+-- MySQL 5.7 / utf8mb4
+
+ALTER TABLE oa_instance
+  ADD COLUMN source_instance_id VARCHAR(64) NULL COMMENT '撤销重提所关联的原实例ID' AFTER status,
+  ADD COLUMN current_round INT NOT NULL DEFAULT 1 COMMENT '当前提交轮次，从1起' AFTER source_instance_id;
+
+-- status 语义：running / returned / completed / rejected / cancelled
+-- returned = 已打回，待发起人修改再提交
+
+ALTER TABLE oa_task
+  ADD COLUMN round_no INT NOT NULL DEFAULT 1 COMMENT '所属提交轮次' AFTER sign_mode;
+
+CREATE TABLE IF NOT EXISTS oa_instance_event (
+  id VARCHAR(64) NOT NULL COMMENT '主键ID',
+  instance_id VARCHAR(64) NOT NULL COMMENT '实例ID',
+  round_no INT NOT NULL DEFAULT 1 COMMENT '轮次',
+  event_type VARCHAR(32) NOT NULL COMMENT 'submit/return/withdraw/complete/reject_end',
+  actor_user_id VARCHAR(64) NULL COMMENT '操作人',
+  task_id VARCHAR(64) NULL COMMENT '关联任务（打回时）',
+  node_key VARCHAR(64) NULL COMMENT '节点key',
+  comment_text VARCHAR(512) NULL COMMENT '意见',
+  tenant_no VARCHAR(64) NOT NULL DEFAULT 'zkxw' COMMENT '租户编号',
+  order_num INT NULL COMMENT '排序号',
+  remark VARCHAR(512) NULL COMMENT '备注',
+  create_by VARCHAR(64) NULL COMMENT '创建人id',
+  create_dept_id VARCHAR(64) NOT NULL DEFAULT '' COMMENT '创建人部门ID',
+  create_time DATETIME NOT NULL COMMENT '创建时间',
+  update_by VARCHAR(64) NULL COMMENT '更新人id',
+  update_time DATETIME NOT NULL COMMENT '更新时间',
+  del_flag SMALLINT NOT NULL DEFAULT 0 COMMENT '删除标记',
+  PRIMARY KEY (id),
+  KEY idx_oa_evt_inst (instance_id, del_flag, create_time)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='OA实例操作事件（进度轴）';