fix(wallet): Save wallet transaction using floor for credits

[rsempe]

This pull request includes several changes to the wallet_transactions services to standardize the handling of credit amounts and improve precision by using BigDecimal and flooring the values to five decimal places.

Standardizing credit amounts:

• app/services/wallet_transactions/create_service.rb: Modified handle_paid_credits, handle_granted_credits, and handle_voided_credits to use BigDecimal for credit amounts, flooring them to five decimal places. [1] [2] [3]
• app/services/wallet_transactions/void_service.rb: Updated the initialize method and removed the credits_amount method to directly use the credits_amount parameter. [1] [2]