fix: prevent MiniClusterCtx race conditions in command shutdown

Capture global MiniClusterCtx into local variables before goroutine/select
evaluation to prevent nil dereference/data race when context is reset to nil
after nil check. Applied to filer, master, volume, and s3 commands.

weed/command/filer.go

@@ -483,8 +483,9 @@ func (fo *FilerOptions) startFiler() {
 		}
 		httpS := newHttpServer(defaultMux, tlsConfig)
 		if MiniClusterCtx != nil {
+			ctx := MiniClusterCtx
 			go func() {
-				<-MiniClusterCtx.Done()
+				<-ctx.Done()
 				httpS.Shutdown(context.Background())
 				grpcS.Stop()
 			}()
@@ -502,8 +503,9 @@ func (fo *FilerOptions) startFiler() {
 		}
 		httpS := newHttpServer(defaultMux, nil)
 		if MiniClusterCtx != nil {
+			ctx := MiniClusterCtx
 			go func() {
-				<-MiniClusterCtx.Done()
+				<-ctx.Done()
 				httpS.Shutdown(context.Background())
 				grpcS.Stop()
 			}()

weed/command/master.go

@@ -311,8 +311,9 @@ func startMaster(masterOption MasterOptions, masterWhiteList []string) {
 			ms.Topo.HashicorpRaft.LeadershipTransfer()
 		}
 	})
-	if MiniClusterCtx != nil {
-		<-MiniClusterCtx.Done()
+	ctx := MiniClusterCtx
+	if ctx != nil {
+		<-ctx.Done()
 		ms.Shutdown()
 		grpcS.Stop()
 	} else {

weed/command/s3.go

@@ -408,8 +408,9 @@ func (s3opt *S3Options) startS3Server() bool {
 			}
 			httpS := newHttpServer(router, tlsConfig)
 			if MiniClusterCtx != nil {
+				ctx := MiniClusterCtx
 				go func() {
-					<-MiniClusterCtx.Done()
+					<-ctx.Done()
 					httpS.Shutdown(context.Background())
 					grpcS.Stop()
 				}()

weed/command/volume.go

@@ -319,10 +319,11 @@ func (v VolumeServerOptions) startVolumeServer(volumeFolders, maxVolumeCounts, v
 		stopChan <- true
 	})
 
-	if MiniClusterCtx != nil {
+	ctx := MiniClusterCtx
+	if ctx != nil {
 		select {
 		case <-stopChan:
-		case <-MiniClusterCtx.Done():
+		case <-ctx.Done():
 			shutdown(publicHttpDown, clusterHttpServer, grpcS, volumeServer)
 		}
 	} else {