Revamp documentation for YouTube Transcript GPT

Updated CHANGELOG, CONTRIBUTING, and USAGE guides to reflect the transition from repo-blueprint to YouTube Transcript GPT. Added detailed instructions for setup, configuration, features, AI integration, proxy support, and contribution guidelines tailored to the new application's functionality and audience.

Author: ukr-projects

docs/CHANGELOG.md

@@ -5,7 +5,7 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## [1.0.0] - 2025-07-25
+## [1.0.0] - 2025-05-19
 
 ### Added
 - 🎉 **Initial release** with core transcript extraction and AI modules