Introduced the SepehrPaymentGateway to replace the previous
payment gateway, AqayePardakht. Added `Rrn` and `DigitalReceipt`
columns to the `PaymentTransactions` table for improved payment
tracking and verification. Updated the Entity Framework model
and mappings to reflect these changes.
Refactored payment transaction logic to support the new gateway,
including creating, verifying, and handling payments. Added new
request/response models for Sepehr gateway integration. Enhanced
error handling and financial statement creation upon successful
payment verification. Removed legacy code and updated dependency
injection for the Parbad library.
