[rust] fluss-rust source release is missing LICENSE and NOTICE

[fresh-borzoni]

Search before asking

• I searched in the issues and found nothing similar.

Description

fluss-rust/scripts/release.sh builds the source tarball with git archive from fluss-rust/, so the archive root is that subdirectory and does not inherit the repo-root LICENSE/NOTICE.
Neither file exists under fluss-rust/, so the tarball ships without either

An ASF source release must contain both, and verifying-a-release-candidate.md
asks verifiers to check them, so the next RC would be voted down.

Willingness to contribute

• I'm willing to submit a PR!