Remove Python bindings (moved to DNLP repository) (#40)

The Python bindings have been relocated to the DNLP repository at
cvxpy/reductions/solvers/nlp_solvers/diff_engine/_bindings/.

This makes diff_engine_core a pure C library, simplifying its build
process and allowing the bindings to be maintained alongside the
rest of the CVXPY/DNLP Python code.

Changes:
- Remove python/ directory (54 files)
- Remove commented Python bindings section from CMakeLists.txt

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: Transurgeon

CMakeLists.txt

@@ -61,25 +61,6 @@ endif()
 # Enable position-independent code for shared library compatibility
 set_property(TARGET dnlp_diff PROPERTY POSITION_INDEPENDENT_CODE ON)
 
-# =============================================================================
-# Python bindings (built when using scikit-build-core)
-# =============================================================================
-#if(SKBUILD)
-#    find_package(Python3 REQUIRED COMPONENTS Interpreter Development.Module NumPy)
-#
-#    # Create Python extension module
-#    Python3_add_library(_core MODULE python/bindings.c)
-#    target_include_directories(_core PRIVATE
-#        ${PROJECT_SOURCE_DIR}/include
-#        ${PROJECT_SOURCE_DIR}/python
-#        ${Python3_NumPy_INCLUDE_DIRS}
-#    )
-#    target_link_libraries(_core PRIVATE dnlp_diff)
-#
-#    # Install to the package directory
-#    install(TARGETS _core LIBRARY DESTINATION dnlp_diff_engine)
-#endif()
-
 # =============================================================================
 # C tests (only for standalone builds)
 # =============================================================================