Move restore to snapshot restore subcommand

Renames the top-level `restore` command to `vaultik snapshot restore`
for consistency with `vaultik snapshot create`. The factory follows the
sibling pattern (newSnapshotRestoreCommand) and its file is renamed to
snapshot_restore.go to match.

internal/cli/entry_test.go

@@ -18,7 +18,7 @@ func TestCLIEntry(t *testing.T) {
 	}
 
 	// Verify all subcommands are registered
-	expectedCommands := []string{"config", "snapshot", "store", "restore", "prune", "info", "version", "remote", "database"}
+	expectedCommands := []string{"config", "snapshot", "store", "prune", "info", "version", "remote", "database"}
 	for _, expected := range expectedCommands {
 		found := false
 		for _, cmd := range cmd.Commands() {
@@ -38,7 +38,7 @@ func TestCLIEntry(t *testing.T) {
 		t.Errorf("Failed to find snapshot command: %v", err)
 	} else {
 		// Check snapshot subcommands
-		expectedSubCommands := []string{"create", "list", "purge", "verify", "cleanup"}
+		expectedSubCommands := []string{"create", "list", "purge", "verify", "cleanup", "restore"}
 		for _, expected := range expectedSubCommands {
 			found := false
 			for _, subcmd := range snapshotCmd.Commands() {