rpc: Fix error wrapping chain in GetAccountLedgerSequence #136

[bilaal441]

What

Fixes the error handling in the GetAccountLedgerSequence function to correctly wrap ErrAccountNotFound, allowing proper error detection in the account sponsorship flow.

Why

Currently, when creating a sponsored account via /tx/create-sponsored-account, the process fails because the error wrapping is incorrect. The error check errors.Is(err, ErrAccountNotFound) fails since the error is returned as a plain string. This fix ensures the error is properly wrapped, allowing correct handling of missing accounts.

Known limitations

N/A

Issue that this PR addresses

Fixes: rpc: Fix error wrapping chain in GetAccountLedgerSequence #136
Priority: High

Checklist

PR Structure

• It is not possible to break this PR down into smaller PRs.
• This PR does not mix refactoring changes with feature changes.
• This PR's title starts with the name of the package most changed in the PR (rpc).

Thoroughness

• This PR adds tests for the new functionality or fixes.
• All updated queries have been tested (refer to this check if the data set returned by the updated query is expected to be same as the original one).

Release

• This is not a breaking change.
• This is ready to be tested in development.
• The new functionality is gated with a feature flag if this is not ready for production.