Task

Add a calculateAnchorFee function to compute fees for anchor transactions.

Details

• Function signature: calculateAnchorFee(amount: string, asset: string, type: TransactionType): Promise<FeeQuote>
• Apply asset-specific fee schedules
• Support flat fee and percentage-based fees
• Return detailed fee breakdown
• Add FeeQuote and TransactionType interfaces

Test

Run pnpm --filter @stellar-pay/anchor-service build to verify no TypeScript errors.