add clang-format config

[ujaandas]

This PR standardizes C++ formatting and linting across the project so editors can format the same way prek does.

• Adds a custom .clang-format file to define code style.
• Updates prek.toml hooks (clang-format, clang-tidy, cppcheck) to:
  • Use the project style (--style=file)
  • Run only on C/C++ source and header files