Add support for Fortran D-notation in scientific input (Fixes #2403)

[Amitjoiya]

Summary

This PR adds support for parsing Fortran-style exponential notation in Scientific mode.
Inputs containing D or d (e.g., 1.073092093D-02) are now treated the same as standard scientific notation using E.

What was changed

• Updated the expression parser to interpret D and d as equivalent to E in scientific notation.
• Added unit tests to verify correct parsing behavior for inputs using D-notation.

Why this is needed

Fortran-based scientific calculations and engineering workflows frequently use D notation.
Supporting this improves compatibility and usability for users working with scientific data.

Validation

• All existing and new unit tests pass.
• No formatting, refactoring, or unrelated code changes were made.

Issue Reference

Fixes #2403