shell: accept a context in the volume move helpers (#10415)

LiveMoveVolume and the copy, tail, delete, mark, replicate, and
configure helpers around it issued every RPC on context.Background(), so
a caller had no way to bound or abort a move once it started. They now
take a context, which the exported LiveMoveVolume in particular needs:
callers outside the shell drive long moves and want to stop them.

The deferred restore in copyVolume runs on a detached, bounded context
rather than the caller's. Marking the source writable again is cleanup,
and cancelling the copy must not skip it and leave the volume readonly —
the same guard balance_task.go already applies for the same reason.

Shell commands pass context.Background(): their Do signature carries no
context, and changing it would touch every command in the package.

Claude-Session: https://claude.ai/code/session_01Ks16jnt4S7gdDk8cheQ3xu

weed/shell/command_volume_delete_empty.go

@@ -1,6 +1,7 @@
 package shell
 
 import (
+	"context"
 	"flag"
 	"io"
 	"log"
@@ -72,7 +73,7 @@ func (c *commandVolumeDeleteEmpty) Do(args []string, commandEnv *CommandEnv, wri
 				if isEmptyVolumeDeleteCandidate(v, quietSeconds, nowUnixSeconds, *collectionPattern) {
 					if *applyBalancing {
 						log.Printf("deleting empty volume %d from %s", v.Id, dn.Id)
-						if deleteErr := deleteVolume(commandEnv.option.GrpcDialOption, needle.VolumeId(v.Id),
+						if deleteErr := deleteVolume(context.Background(), commandEnv.option.GrpcDialOption, needle.VolumeId(v.Id),
 							pb.NewServerAddressFromDataNode(dn), true, false); deleteErr != nil {
 							err = deleteErr
 						}