Draft: Prepare python interface for clive - show layer

Summary

First part of the Python Interface (PY) implementation, focusing on show operations.

Changes:

• Add PY core infrastructure (exceptions, validators, data classes)
• Add PY show commands (profiles, balances, accounts, witnesses, authority)
• Add PY configure and generate interfaces
• Add PY base classes with public API (from clive.py import ...)
• Integrate CLI show commands with PY layer

What works:

from clive.py import ClivePy, UnlockedClivePy, clive_use_unlocked_profile

async with clive_use_unlocked_profile() as clive:
    balances = await clive.show.balances("alice")
    accounts = await clive.show.accounts()
    witnesses = await clive.show.witnesses("alice")
    authority = await clive.show.owner_authority("alice")

What's stubbed (for next MR):

• clive.process - raises NotImplementedError