Remove unused imports from rbf-service.ts

[jamespepper81]

Description

Clean up unused imports in the RBF service module. This PR removes four unused function imports from ecc-utils.ts that are no longer referenced in the codebase, along with an obsolete comment.

Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📚 Documentation update
• 🎨 UI/UX improvement
• ♻️ Code refactoring (no functional changes)
• ⚡ Performance improvement
• 🔒 Security improvement
• 🧪 Test coverage improvement
• 🔧 Build/CI improvement

Changes Made

• Removed unused import: validateECCLibrary
• Removed unused import: deriveAddressIndexFromAddress
• Removed unused import: findNextUnusedAddressIndex
• Removed obsolete comment referencing validateECCLibrary
• Kept necessary imports: validateECCLibraryFull, estimateTransactionSize, deriveAddressIndexAndChainFromAddress, and generateCancellationAddress

Testing Performed

Automated Testing

• Linting passes
• No compilation errors
• All existing tests pass

Checklist

• My code follows the project's code style guidelines
• I have performed a self-review of my own code
• My changes generate no new warnings or errors

Additional Notes

This is a straightforward cleanup to improve code maintainability by removing dead imports that are not used anywhere in the rbf-service.ts module.

https://claude.ai/code/session_016Cs3ckjXRRHT6eX6JYLmXq