fix(worker): 统一异步执行准入范围

Worker 执行阶段重建准入范围时遗漏 worker_capacity，导致已预留 River 槽的任务再次同步等待准入并占住执行槽。

调度、执行和候选切换统一复用 taskAdmissionScopes，确保异步任务始终携带同一全局 Worker 容量范围。

验证：Go 全量测试、runner race、go vet、迁移安全检查通过。

apps/api/internal/runner/service.go

@@ -544,8 +544,10 @@ func (s *Service) executeWithToken(ctx context.Context, task store.GatewayTask,
 	var admittedLeases []store.ConcurrencyLease
 	admittedPlatformModelID := ""
 	if distributedAdmission && len(candidates) > 0 {
-		admissionScopes, groupID := s.admissionScopes(ctx, user, candidates[0])
-		admissionScopes = acceptanceAdmissionScopes(task, admissionScopes)
+		admissionScopes, groupID, scopeErr := s.taskAdmissionScopes(ctx, task, user, candidates[0])
+		if scopeErr != nil {
+			return Result{}, scopeErr
+		}
 		hasConcurrentLimit := false
 		for _, scope := range admissionScopes {
 			if scope.ConcurrentLimit > 0 {