Optimize fibonacci implementation and add unit tests

[nborges-aws]

Fibonacci Implementation Optimization and Test Coverage

Overview

This PR improves the Fibonacci number calculation implementation and adds comprehensive unit tests. The changes include:

• Optimizing the Fibonacci algorithm from recursive to iterative approach using dynamic programming
• Adding unit tests for both the add and fibonacci functions
• Improving code readability with better type hints

Benefits

• Better performance by eliminating recursive calls
• Reduced stack memory usage
• Added test coverage to ensure reliability
• Improved code maintainability

Testing

New unit tests verify:

• Basic addition operations
• Edge cases for Fibonacci sequence (0, 1)
• Various Fibonacci sequence positions