Create a unique ``config.yaml`` file

### 📝 Description of the feature

Following @germa89's [comment](https://github.com/ansys/mapdl-cmd-conv/pull/164#discussion_r2192412432), we should use a unique config file instead of having two similar ones.

### 💡 Steps for implementing the feature

_No response_

### 🔗 Useful links and references

_No response_

Start by reviewing the repository's two similar configuration files and the referenced discussion in PR 164. Determine which settings must be retained in the unique config.yaml, then verify that the relevant conversion and documentation workflows use the consolidated file without regressions.

Written by the indexing model from the issue text.