refactor(plugin): rename detection_interval_seconds → detection_interval_minutes (#9366)

Minutes is the natural granularity for detection cadence — every
production handler already set the seconds field to a 60-multiple
(17*60, 30*60, 3600, 24*60*60). Switching to minutes drops the *60
arithmetic and matches the unit conventions used elsewhere in the
plugin worker forms.

- Proto: AdminRuntimeDefaults + AdminRuntimeConfig.detection_interval_*
  field renamed.
- Helpers: durationFromMinutes / minutesFromDuration alongside the
  existing seconds variants in plugin_scheduler.go.
- Handlers: vacuum, ec_balance, balance, erasure_coding, iceberg,
  admin_script, s3_lifecycle now declare DetectionIntervalMinutes.
- Admin: scheduler_status + types + UI templ + plugin_api.go pass
  through the new field; UI label and table cells switch to "min".

weed/admin/dash/plugin_api.go

@@ -936,8 +936,8 @@ func applyDescriptorDefaultsToPersistedConfig(
 	if descriptor.AdminRuntimeDefaults != nil {
 		runtime := config.AdminRuntime
 		defaults := descriptor.AdminRuntimeDefaults
-		if runtime.DetectionIntervalSeconds <= 0 {
-			runtime.DetectionIntervalSeconds = defaults.DetectionIntervalSeconds
+		if runtime.DetectionIntervalMinutes <= 0 {
+			runtime.DetectionIntervalMinutes = defaults.DetectionIntervalMinutes
 		}
 		if runtime.DetectionTimeoutSeconds <= 0 {
 			runtime.DetectionTimeoutSeconds = defaults.DetectionTimeoutSeconds