refactor: use services layer and modularize transfer operations

Decouple CLI commands from internal helper logic and consolidate the
core file transfer operations in the service layer to improve library
portability.

- Make MdrsClient subclass MdrsService to inherit resource resolution.
- Remove all deprecated helper methods from BaseCommand.
- Move core upload and download logic to a new transfer module.
- Refactor all CLI commands to route actions through MdrsClient.
- Eliminate circular imports between client and CLI command modules.

mdrsclient/commands/logout.py

@@ -21,8 +21,8 @@ class LogoutCommand(BaseCommand):
 
     @classmethod
     def logout(cls, remote: str) -> None:
-        remote_host = cls._parse_remote_host(remote)
         from mdrsclient.client import MdrsClient
 
+        remote_host = MdrsClient.parse_remote_host(remote)
         client = MdrsClient.from_remote(remote_host)
         client.logout()