- Add README.md with installation instructions, architecture overview, and API examples for all SDK modules
- Refactor TelecomSDK::Client to use modular API clients (SubscriberAPI, UsageAPI, PaymentAPI, RatingPlanAPI, SystemAPI, GraphQLAPI)
- Add AuthProvider class with API key and JWT token support (generate_jwt_token, validate_jwt_token methods)
- Add HTTPClient base class with retry