[Logic] Implement dynamic fee structure for vault operations

[AbelOsaretin]

Description

Currently, there are no fees for deposits, withdrawals, or funding. A fee structure would:

• Generate revenue for protocol maintenance
• Discourage高频 trading
• Fund protocol development

Recommendation

• Add configurable fee percentages for deposit/withdrawal
• Add a fee_recipient address
• Implement fee collection in deposit/withdraw functions
• Add admin functions to update fee parameters

Severity

Low — Business model consideration.