Implement `entity/withdraw` for pool withdrawal

[amytsang]

Description: Create an entity to handle withdrawal operations from pools.

Subtasks:

• Set up the withdraw entity folder structure following FSD principles
• Implement a Tanstack Query useMutation hook for withdrawal operations
• Create TypeScript interfaces for withdrawal parameters and results
• Use Viem for transaction creation and sending
• Implement BigDecimal for precise withdrawal amount calculations
• Develop utility functions for withdrawal-related operations