Merge patch series "rust: file: mark `LocalFile` as `repr(transparent)`"

Mark files as repr(transparent) to ensure identical layout between C and Rust.

* patches from https://lore.kernel.org/20250527204636.12573-1-pekkarr@protonmail.com:
  rust: file: improve safety comments
  rust: file: mark `LocalFile` as `repr(transparent)`

Link: https://lore.kernel.org/20250527204636.12573-1-pekkarr@protonmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>