added calculateAnchorFee function

[DokaIzk]

Description

Implemented the calculateAnchorFee function in the @stellar-pay/anchor-service package to compute fees for anchor transactions. This includes adding the FeeQuote interface for detailed fee breakdowns and the TransactionType enum to support deposit, withdrawal, and transfer operations. Asset-specific fee schedules (e.g., USDC, XLM) have been configured to apply both flat and percentage-based fees.

Fixes #86

Type of change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Verified that the newly added TypeScript interfaces and logic compile successfully without any type errors across the workspace.

• Built the @stellar-pay/anchor-service package using pnpm --filter @stellar-pay/anchor-service build

Test Configuration:

• Firmware version: N/A
• Hardware: N/A
• SDK: Node.js / pnpm workspace

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

closes: #86

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[DokaIzk]

@MissBlue00 Please kindly review

[MissBlue00]

@DokaIzk the ci/cd checks failed and there are merge conflicts, please resolve

[DokaIzk]

@MissBlue00 fixed the conflicts, awaiting workflow approval for CI checks