Add schemas and models for every endpoint

[MojtabaOnTheNet]

Add Schemas and Models for All Endpoints

Introduce a structured data layer for the banking system by defining Pydantic schemas and database models for every API endpoint in the application.

This includes models and schemas for core banking features such as:

• User authentication (register, login, token handling)
• Account management
• Deposits and withdrawals
• Loan creation, approval, and repayment
• Transaction history and tracking

Each endpoint should have:

• Database models (SQLAlchemy or ORM equivalent) to define persistent structure
• Request schemas to validate incoming data
• Response schemas to control and standardize API outputs

This ensures strong type safety, clear API contracts, and better separation between internal database structure and external API communication.