Reorganized the genai package by removing legacy LLM-related files and introducing a new modular interface under the 'interface' directory. Added provider-specific model classes, centralized constants, and updated the example to use the new API and data structures. Updated exports in genai.dart and improved dependency management.
Renamed the example directory to genai_example, updated package name in pubspec.yaml, and added pubspec_overrides.yaml for local dependency overrides. Updated pubspec.lock to reflect new and overridden dependencies.
