Introduces a new PHP client SDK generated via OpenAPI for the Lethean blockchain, including source code, models, API classes, documentation, tests, and configuration files. Updates Makefile to support PHP SDK generation and modifies php.json package configuration.
Added linguist-generated attribute for SDK clients in .gitattributes to hide them in GitHub diffs. Enhanced utils/sdk/Makefile with target-specific hooks, improved ignore file handling, and refined Go client build steps. Updated Go SDK config to use 'lthn' as package name and set isGoSubmodule property.
