Add functional tests for PY show layer

Tests for Python Interface show operations:
- TestShowProfiles: Verifies profiles listing
- TestShowBalances: Verifies balance retrieval with Balances dataclass
- TestShowAccounts: Verifies accounts information with Accounts dataclass
- TestShowWitnesses: Verifies witness listing with WitnessesResult
- TestShowAuthority: Verifies owner/active/posting authority with AuthorityInfo
- TestProcessStubbed: Verifies process raises NotImplementedError

All tests use the PyWorld fixture that connects to test beekeeper.