Add EUR bank percent fee with separate fee breakdown

[TaprootFreak]

Summary

• Add new Bank fee: 0.5% on all EUR bank payments (migration, fiat id 2)
• Add bankFixed and bankPercent fields to FeeDto API response for separate display
• Existing bank field remains as sum (backwards compatible)
• Historical transactions return null for the new breakdown fields

Changes

• FeeDto — new optional fields bankFixed, bankPercent
• calculateTotalFee() — compute and return breakdown
• getTargetEstimation() / getTxFeeInfos() — propagate new fields
• TransactionDtoMapper.mapFees() — return null for historical data
• Migration 1773700400000-AddEurBankPercentFee — insert new Bank fee row

Test plan

• Verify migration runs on staging
• GET /buy/quote with EUR input — confirm bankFixed and bankPercent are separate in response
• GET /buy/quote with CHF input — confirm bankPercent is 0 (no EUR fee)
• GET /history — confirm bankFixed and bankPercent are null for old transactions
• Verify bank field still equals bankFixed + bankPercent