feat(flow): 用户面四查询(todo/done/cc/my)支持 appKey 按应用筛选

工作台四页签加「按应用筛选」：controller 收可选 appKey，经 FlowQueryService
透传到分页查询；口径=办件定义归属 flw_def.app_key（join flw_instance→flw_def，
均多对一，不影响已办「一个办件一行」的去重与分页）。appKey 空串按不过滤处理
(emptyToNull)，避免清筛选后误成空列表。FlwCcRepository 抄送派生查询相应改
@Query 以支持 join 过滤；FlowEngineIT 两处调用补 null 实参。

门禁：mvn compile/test-compile ✓ + 非 DB 单测 44 例 ✓；本机无 MySQL(3306
未监听)，新 JPQL 未在真实库执行，FlowEngineIT/OapiFlowContractIT 待有库环境补跑

src/main/java/com/yunhai/flowcenter/controller/api/FlowUserController.java

@@ -45,33 +45,37 @@ public class FlowUserController {
     @GetMapping("/my")
     public BasePageResult<FlowModels.InstanceItem> my(BoaUser user,
                                                       @RequestParam(value = "status", required = false) Integer status,
+                                                      @RequestParam(value = "appKey", required = false) String appKey,
                                                       @RequestParam(value = "page", required = false) Integer page,
                                                       @RequestParam(value = "size", required = false) Integer size) {
-        return queryService.pageMy(requireSchId(user), user.getId(), status, page, size);
+        return queryService.pageMy(requireSchId(user), user.getId(), status, appKey, page, size);
     }
 
     /** 我的待办（主路径，走 assignee 索引） */
     @GetMapping("/todo")
     public BasePageResult<FlowModels.TaskItem> todo(BoaUser user,
+                                                    @RequestParam(value = "appKey", required = false) String appKey,
                                                     @RequestParam(value = "page", required = false) Integer page,
                                                     @RequestParam(value = "size", required = false) Integer size) {
-        return queryService.pageTodo(requireSchId(user), user.getId(), page, size);
+        return queryService.pageTodo(requireSchId(user), user.getId(), appKey, page, size);
     }
 
     /** 我的已办 */
     @GetMapping("/done")
     public BasePageResult<FlowModels.TaskItem> done(BoaUser user,
+                                                    @RequestParam(value = "appKey", required = false) String appKey,
                                                     @RequestParam(value = "page", required = false) Integer page,
                                                     @RequestParam(value = "size", required = false) Integer size) {
-        return queryService.pageDone(requireSchId(user), user.getId(), page, size);
+        return queryService.pageDone(requireSchId(user), user.getId(), appKey, page, size);
     }
 
     /** 我的抄送（NOTIFY 节点落库；知会不占待办，独立页签） */
     @GetMapping("/cc/my")
     public BasePageResult<FlowModels.CcItem> ccMy(BoaUser user,
+                                                  @RequestParam(value = "appKey", required = false) String appKey,
                                                   @RequestParam(value = "page", required = false) Integer page,
                                                   @RequestParam(value = "size", required = false) Integer size) {
-        return queryService.pageCc(requireSchId(user), user.getId(), page, size);
+        return queryService.pageCc(requireSchId(user), user.getId(), appKey, page, size);
     }
 
     /** 办件详情（提交人/办理人/本校管理员可见） */