Feature Request: Add a way to check the account balance easily

### Is your feature request related to a problem? Please describe.

The Base Account SDK doesn’t currently have a simple way to check the account balance. Adding this feature would make it easier for developers to get balance information directly.
Right now, developers need to set up their own logic to check the account balance, which can be a hassle. A built-in method would simplify this and make things more consistent.

## Proposed Solution
Add a method like `getAccountBalance()` to the SDK, making it simple to retrieve the account balance.

The issue names no files, tests, or entry points. Start by locating the SDK's account-related API and existing account data methods; clarify the balance source, return shape, error behavior, and tests needed to establish when the feature is done.

Written by the indexing model from the issue text.