Create a utilities module for interacting with KiiChain

[Thaleszh]

Is your feature request related to a problem? Please describe.
Common operations like address formatting, Bech32 conversion, and pubkey serialization aren’t available yet, leading to boilerplate in user applications.

Describe the solution you'd like

• Add a utils/ module or crate that includes:

  • Bech32 address parsing and validation
  • Conversion between EVM hex and Cosmos address formats
  • Gas estimation and fee calculation helpers
  • Timestamp or chain ID utilities

• Write unit tests for each helper

Describe alternatives you've considered
Leaving utilities to downstream apps, but having them in SDK improves consistency and dev experience.

Additional context
This module could mirror the @kiichain/kiijs-utils JavaScript package.