[✨ Feature request]: define internal forces class with coordinate system for all strenth/stability checks

[GerjanDorgelo]

Description

Create a reusable internal forces class that establishes a clear, documented coordinate system for representing internal forces and moments. This class should serve as a standardized input for all structural strength and stability checks across the blueprints library (steel, concrete, timber sections, etc.).

Proposal to deviate from coordinate system used in sectionproperties, and make it such that z is vertical. This alligns better with common software like SCIA Engineer. sectionproperties has a feature request that alligns their properties with what is presented here.

                z (vertical, usually strong axis)
                ↑
                |     x (longitudinal beam direction, into screen)
                |    ↗
                |   /
                |  /
                | /
                |/
      ←---------O
       y (horizontal/side, usually weak axis)

Acceptance Criteria

• [] code
• [] tests

Dependencies

No response

Confirmation

• I have checked that this feature does not already exist in the issue tracker.
• I have read and understood the contribution guidelines.