Example php

[cabelo]

Add PHP FFI examples for libzupt

• Add a reusable PHP FFI wrapper for the libzupt C ABI
• Add examples for in-memory encryption, file encryption, key management, random byte generation, hashing, and secure buffers
• Add automatic shared library path detection with support for LIBZUPT_PATH
• Add a script to run all PHP examples
• Add English documentation with build, configuration, usage, security, and platform notes
• Document the current hybrid key and encryption header sizes
• Prevent execution on Windows until the ABI exposes a portable memory-release function