This commit introduces Doxygen for documentation generation and a Gitea
workflow for continuous integration.
- Adds a `Doxyfile` to configure Doxygen to build a documentation
website with diagrams.
- Updates `AGENTS.md` to require Doxygen-compatible comments for all
code.
- Adds Doxygen comments to existing C++ source files to comply with
the new standard.
- Creates a Gitea workflow (`.gitea/workflows/build.yml`) that:
- Builds the project on every push.
- Generates Doxygen documentation.
- Uploads the compiled library and the documentation website as
artifacts.
- Rename all files, directories, and internal project names to "MedicalLib".
- Replace the generic `add` function with a more domain-specific `calculateBMI` function as an initial example of the library's capabilities.
- Update the `AGENTS.md` file to describe the new purpose and scope of the MedicalLib library.