feat: 发起时指派——assignPolicy 配置/assign_json 快照/引擎收窄/preview+apply 契约

src/main/java/com/yunhai/flowcenter/controller/oapi/OapiFlowController.java

@@ -62,6 +62,13 @@ public class OapiFlowController {
         return flowService.apply(schId, appKey, body);
     }
 
+    /** 发起预览：返回开启发起时指派的节点与候选人（已剔除发起人本人），供子应用提交页选人 */
+    @GetMapping("/apply/preview")
+    public OapiModels.ApplyPreviewVo applyPreview(@RequestParam("schId") Long schId,
+            @RequestParam("flowGuid") String flowGuid, @RequestParam("submitterId") Integer submitterId) {
+        return flowService.applyPreview(schId, flowGuid, submitterId);
+    }
+
     @GetMapping("/instance")
     public OapiModels.InstanceVo instance(@RequestParam("bizType") String bizType,
                                           @RequestParam("bizId") String bizId,