feat(oa): add oa_instance.initiator_select_json for per-node self-select

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

backend/app/models/models.py

@@ -855,6 +855,7 @@ class OaInstance(Base):
     initiator_user_id = Column(String(64), nullable=False, comment="发起人")
     initiator_dept_id = Column(String(64), nullable=True, comment="发起人部门")
     form_data_json = Column(Text, nullable=True, comment="表单数据 JSON")
+    initiator_select_json = Column(Text, nullable=True, comment="发起人自选 JSON {nodeId:[userId,...]}")
     status = Column(
         String(32),
         nullable=False,

docs/sql/patch_2026-07-23_oa_instance_initiator_select_json.sql

@@ -0,0 +1,4 @@
+-- OA 实例：按节点持久化发起人自选（nodeId -> userId[]）
+ALTER TABLE oa_instance
+  ADD COLUMN initiator_select_json TEXT NULL COMMENT '发起人自选 JSON {nodeId:[userId,...]}'
+  AFTER form_data_json;