bug: Key management commands ignore keyring configuration from config file

[samricotta]

When using key management commands (e.g., covenant-signer keys list), the CLI ignores keyring settings from the config file. For example, even with keyring-backend = "file" set in the config, users must still provide --keyring-backend file on the command line.

Current behavior:

# Config file has keyring-backend = "file"
covenant-signer keys list  # Fails
covenant-signer keys list --keyring-backend file  # Works

Expected behavior:

# Config file has keyring-backend = "file"
covenant-signer keys list  # Should work using config settings