Cardano Updates

- Normalized transaction hash to lowercase for consistency.
- Introduced witness summaries for better tracking of signatures and public keys.
- Improved transaction hash validation and error handling for provided transaction hashes.
- Refactored transaction state management and updated transaction JSON structure to include multisig details.
- Enhanced error responses for better clarity on transaction submission issues.

   Remove conditional compilation, OnceLock pattern, and unnecessary complexity to clearly show the 4-step IPFS PubSub workflow.

Replaces IsCardanoEra constraint with Exp.IsEra in ToJSON instances
for TxOut and UTxO types, adopting the new experimental Era framework
for JSON serialization. This change simplifies the era handling by
using Exp.useEra instead of cardanoEra and reduces the pattern matching
cases in txOutToJsonValue to only handle ConwayEra and DijkstraEra.

- Update TxOut ToJSON instance to use Exp.IsEra constraint
- Update UTxO ToJSON instance to use Exp.IsEra constraint
- Refactor txOutToJsonValue to use Exp.Era type parameter
- Remove redundant pattern matches for Byron through Babbage eras
- Update test generators to use ShelleyBasedEraConway instead of Babbage

The test suite changes ensure compatibility with the new era handling
approach by testing against the Conway era, which provides better
coverage of the current serialization logic.

build(deps): bump actions/checkout from 5 to 6

   demonstrate the 4-step workflow.