Plugin scheduler: sequential iterations with max runtime (#8496)

* pb: add job type max runtime setting

* plugin: default job type max runtime

* plugin: redesign scheduler loop

* admin ui: update scheduler settings

* plugin: fix scheduler loop state name

* plugin scheduler: restore backlog skip

* plugin scheduler: drop legacy detection helper

* admin api: require scheduler config body

* admin ui: preserve detection interval on save

* plugin scheduler: use job context and drain cancels

* plugin scheduler: respect detection intervals

* plugin scheduler: gate runs and drain queue

* ec test: reuse req/resp vars

* ec test: add scheduler debug logs

* Adjust scheduler idle sleep and initial run delay

* Clear pending job queue before scheduler runs

* Log next detection time in EC integration test

* Improve plugin scheduler debug logging in EC test

* Expose scheduler next detection time

* Log scheduler next detection time in EC test

* Wake scheduler on config or worker updates

* Expose scheduler sleep interval in UI

* Fix scheduler sleep save value selection

* Set scheduler idle sleep default to 613s

* Show scheduler next run time in plugin UI

---------

Co-authored-by: Copilot <copilot@github.com>

weed/plugin/worker/admin_script_handler.go

@@ -111,6 +111,7 @@ func (h *AdminScriptHandler) Descriptor() *plugin_pb.JobTypeDescriptor {
 			PerWorkerExecutionConcurrency: 1,
 			RetryLimit:                    0,
 			RetryBackoffSeconds:           30,
+			JobTypeMaxRuntimeSeconds:      1800,
 		},
 		WorkerDefaultValues: map[string]*plugin_pb.ConfigValue{},
 	}