Improved handling of different value cases and null values and added test classes.

Updated “sqrt()” method in Complex class to accurately handle scenarios where x coordinate is negative and y coordinate is zero, avoiding incorrect zero vector or NaN returns.

Enhanced transform method in JuliaTransform class to handle different coordinate cases using the 'sign' field, providing flexibility to choose between positive or negative square root signs.

Added test classes (ComplexTest, Vector2DTest, JuliaTransformTest) to validate both negative and positive scenarios, to ensure correct calculations.