Currency on Account

**Is your feature request related to a problem? Please describe.**
The current account model lacks currency support, making it difficult to handle multi-currency accounts. This could be problematic for future expansion in regions with different currencies.

**Describe the solution you'd like**
Introduce a Currency model that allows accounts to be linked to different currencies. This will enable the application to support multi-currency accounts and transactions.

**Describe alternatives you've considered**
Adding a simple currency field to the account model without a full currency entity.

**Additional context**
This feature would future-proof the application for international usage. It could also open the door to additional features like currency conversion, exchange rate tracking, and multi-currency balances.