feat: add one-command install scripts and automated release pipeline

[liangshaoteng]

• .github/workflows/release.yml: triggered on git tag vX.Y.Z; builds linux-x86_64, linux-aarch64, and windows-x64 packages, generates a combined SHA256SUMS, and publishes a GitHub Release via softprops/action-gh-release. workflow_dispatch is also supported for dry-run packaging without cutting a release.
• scripts/install.sh: Linux one-command installer. Detects x86_64 or aarch64, fetches the matching tarball from GitHub Releases, verifies SHA256, extracts to --prefix (default /usr/local), and finishes with ldconfig plus symlinks under /usr/local/lib.
• scripts/install.ps1: Windows x64 one-command installer. Verifies SHA256, installs to %ProgramFiles%\LinkerHand\cpp-sdk (overridable), appends the prefix to the user's CMAKE_PREFIX_PATH, and offers an optional -AddToPath switch.
• CMakeLists.txt: introduces the LINKERHAND_SDK_VERSION cache variable (default 2.0.0) so CI can inject the git tag via -DLINKERHAND_SDK_VERSION=, keeping tag, tarball filename, and CMake config version in sync.
• cmake/linkerhand-cpp-sdk-config-version.cmake becomes a .cmake.in template; configure_file writes the versioned copy before install.
• README.md: adds a one-command install section at the top of the quick-start guide (Linux and Windows).
• INSTALL.md: new document covering installation, version pinning, offline install, uninstall, and FAQ for downstream users.