Install the Python module and binaries with pip

[mikelangmayr]

Stacked on #23, so the diff shows only the packaging work. Retarget to main once #23 merges.

• Add pyproject.toml using scikit-build-core, so pip install ./camera-interface compiles camera_interface into site-packages and puts camerad and its tools on the environment's PATH. CONTROLLER defaults to archon and BUILD_PYTHON_MODULE is forced on; any other CMake option passes through as --config-settings=cmake.define.X=Y
• pybind11 moves into [build-system] requires, so pip fetches it into an isolated build environment rather than the user installing it by hand
• Derive PROJECT_BASE_DIR from CMAKE_CURRENT_SOURCE_DIR instead of $ENV{PWD}/../. A build backend invokes cmake with cwd=, which does not update PWD, so the old form failed the configure outright with add_subdirectory given source "/tmp/..//camerad". Identical for the existing cd build && cmake .. flow
• Send install rules to SKBUILD_SCRIPTS_DIR/SKBUILD_PLATLIB_DIR under a wheel build and to the GNU prefix layout otherwise, since a wheel needs the module importable as a top-level name and the binaries on PATH
• Keep CMake's outputs in the build directory under a wheel build, so a pip install does not write into the source tree's bin/
• Document the pip flow in the README
• Verified by pip install into a scratch venv: the module imports from site-packages with PYTHONPATH unset and reports hispec_tracking_camera/archon, and open, load, power on, expose 1 all return DONE against the emulator using only the venv's binaries