[C++] Add release workflow and cut the 0.1.0 release

Context

The C++ SDK landed in #415. Its distribution model is CMake + GitHub Releases only — no package manager (no Conan/vcpkg) — mirroring the C FFI. The installable CMake package (find_package(zerobus) + bundled FFI archive) is in place; what's missing is the release automation and the first release itself.

Tasks

• Add release-zerobus-sdk-cpp.yml in databricks/secure-public-registry-releases-eng, modeled on release-zerobus-sdk-ffi.yml: per-platform matrix → cmake --install into a staging tree → archive (headers + libzerobus_cpp + bundled libzerobus_ffi + the find_package config) → security scan → attach the per-platform archives to a GitHub Release.
• Add the CODEOWNERS entry for the new workflow (@databricks/zerobus-admin).
• Decide the platform matrix — match the FFI's (linux gnu/musl x86_64/aarch64, windows) or a chosen subset.
• Write the 0.1.0 entry in cpp/CHANGELOG.md (version already set and in sync across version.hpp and CMakeLists.txt).
• Cut the release: an FFI release (ffi/v*) must precede cpp/v* since the archive bundles the FFI; then tag cpp/v0.1.0 to trigger the workflow.

Notes

• No new platform capability is required: GitHub-Release publishing and per-platform artifact builds already exist for the FFI, so this follows an established pattern.
• Related: #415

/cc @databricks/zerobus-admin