Migrate build system from qmake to CMake:

- Replace `openfortigui.pro` with `CMakeLists.txt` for modernized build and dependency management.
- Update `debian/rules` to use CMake (`--buildsystem=cmake`) for streamlined builds.
- Ensure versioning consistency via `project(... VERSION ...)` in CMake.
- Adapt related scripts and tests to reflect the build system change.
- Remove legacy qmake configurations and update Debian package dependencies (`cmake` added to `control`).