chore: prepare Apache Paimon C++ 0.2.3 release

[zjw1111]

Purpose

Linked issue: N/A

Prepare the Apache Paimon C++ 0.2.3 source release and complete the documentation and example alignment needed after the repository migration.

• set the project and documentation version to 0.2.3
• update documentation links and the version selector for the Apache website
• align the README, user guides, public comments, CI configuration, and examples with the current implementation
• remove obsolete Git LFS setup from documentation and CI
• clarify dependency-source, static-library, FileStoreCommit, and CommitMessage usage
• make the examples support both shared and static Arrow packages
• add deterministic source archive creation with SHA-512 checksum and optional detached OpenPGP signing
• add release-candidate verification for signatures, checksums, archive layout, release metadata, compiled artifacts, file permissions, Apache RAT, and release builds/tests

The scripts only create and verify release artifacts. They do not create tags, publish artifacts, or modify Apache distribution repositories.

Tests

• pre-commit checks for all changed release-preparation files
• shell syntax validation for both release scripts
• JSON validation for docs/source/_static/versions.json
• generated two source archives from the same commit and verified they were byte-identical
• generated and verified a detached OpenPGP signature with an isolated test keyring
• Apache RAT 0.16.1 verification on the generated source archive
• full Release build and test from the extracted source archive (25/25 CTest groups passed)
• README and example CMake builds
• Sphinx lint and warning-as-error HTML build
• Doxygen generation and clang-format dry run
• git diff --check upstream/main

API and Format

No API signature, storage format, or protocol changes. Public comments were updated to describe the current behavior.

Documentation

The documentation now points to the Apache Paimon C++ website, reports version 0.2.3, and includes instructions for creating and verifying a release candidate.

Generative AI tooling

Generated-by: Codex (GPT-5)

[lxy-9602]

+1

[lucasfang]

+1