PR: IFC export ignores mapping table setting for certain built-in parameters

### Problem Description

When exporting IFC with user-defined property sets, some parametes are ignored and repalced with buil-in ones. Seems to problem wehn using user parameters with same names as built-in ones (ignores case). In example below I try to export OBJEM (Volume) and PLOCHA (Area) shared parameters but the values are replaced with built-in parameters Objem (Volume) and Plocha (Area). No matter how I configure the TXT file. Use of type parameters in instance proeprty sets is checked.

See attachment (project, family, mapping table, shared parameters).

[ifc_export_issue.zip](https://github.com/user-attachments/files/30226836/ifc_export_issue.zip)

### Revit Version

2025.4.x

### IFC for Revit Addon Version

25.4.40

### Windows Version

11 25H2

Start by reproducing the IFC export with the attached ifc_export_issue.zip, focusing on the mapping TXT and the OBJEM/PLOCHA shared parameters in Revit 2025.4.x with IFC for Revit 25.4.40. Compare the exported properties with the mapping-table configuration; done means user-defined values are retained instead of being replaced by case-insensitive built-in parameters.

Written by the indexing model from the issue text.