fix(plugin): remove Min Volume Age field from vacuum plugin worker config (#9095)

* fix(plugin): remove Min Volume Age field from vacuum plugin worker config

The min_volume_age_seconds setting is not needed as a user-configurable
field in the plugin worker form. The detection logic continues to use
the hardcoded default from NewDefaultConfig().

* fix(plugin): disable volume age filtering in plugin worker detection

Set MinVolumeAgeSeconds to 0 in deriveVacuumConfig so the plugin worker
does not filter out volumes by age during detection.

* fix(plugin): remove all volume age filtering from plugin worker detection

Remove age-related fields from detection trace messages, activity
reports, and per-volume diagnostics. The plugin worker now only
filters by garbage threshold.

weed/plugin/worker/vacuum_handler_test.go

@@ -84,18 +84,12 @@ func TestDeriveVacuumConfigAllowsZeroValues(t *testing.T) {
 		"garbage_threshold": {
 			Kind: &plugin_pb.ConfigValue_DoubleValue{DoubleValue: 0},
 		},
-		"min_volume_age_seconds": {
-			Kind: &plugin_pb.ConfigValue_Int64Value{Int64Value: 0},
-		},
 	}
 
 	cfg := deriveVacuumConfig(values)
 	if cfg.GarbageThreshold != 0 {
 		t.Fatalf("expected garbage_threshold 0, got %v", cfg.GarbageThreshold)
 	}
-	if cfg.MinVolumeAgeSeconds != 0 {
-		t.Fatalf("expected min_volume_age_seconds 0, got %d", cfg.MinVolumeAgeSeconds)
-	}
 }
 
 func TestMasterAddressCandidates(t *testing.T) {
@@ -174,7 +168,7 @@ func TestEmitVacuumDetectionDecisionTraceNoTasks(t *testing.T) {
 	sender := &recordingDetectionSender{}
 	config := vacuumtask.NewDefaultConfig()
 	config.GarbageThreshold = 0.3
-	config.MinVolumeAgeSeconds = int((24 * time.Hour).Seconds())
+	config.MinVolumeAgeSeconds = 0
 
 	metrics := []*workertypes.VolumeHealthMetrics{
 		{