feat: implement cmd management for targets, LUNs, and TPGTs (fixes #36)

- Fix target delete URL path mismatch (/targets/ -> /target/)
- Implement target create/delete server handlers with proper validation
- Add DeleteTarget method with force flag and mutex locking to SCSITargetService
- Implement full LU management: create/list/delete through CLI, client, and server
- Add TPGT list command to show target portal group tags
- Add unit tests for target/LU router handlers and SCSI service

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pkg/api/client/target_delete.go

@@ -29,7 +29,7 @@ func (cli *Client) TargetRemove(ctx context.Context, options api.TargetRemoveOpt
 	if options.Force {
 		query.Set("force", "1")
 	}
-	resp, err := cli.delete(ctx, "/targets/"+options.Name, query, nil)
+	resp, err := cli.delete(ctx, "/target/"+options.Name, query, nil)
 	ensureReaderClosed(resp)
 	return err
 }