feat(contract): add event and error decoding to Interface

[dlr-a]

Motivation

Interface currently only supports function encoding/decoding. A // TODO: events/errors comment marked the missing implementation. This PR adds decoding support for events and errors.

Solution

• Add events and errors lookup maps to Interface (parallel to the existing functions map).
• Add decode_event / decode_event_with_selector and decode_error / decode_error_with_selector public methods.
• Add corresponding get_event_from_name, get_event_from_selector and get_error_from_name, get_error_from_selector helpers.
• Add UnknownEvent, UnknownEventSelector, UnknownAbiError, UnknownAbiErrorSelector variants to Error.
• Add tests covering happy-path roundtrips, unknown-name/selector errors, and malformed data.

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes