AI Library Migration to Firebase Genkit and Improvements

[Gerifield]

The merge request transitions the project to the Firebase Genkit framework, providing a more robust and pluggable architecture for AI interactions.

Key improvements included in this submission:

1. Framework Migration: Switched to Firebase Genkit, which simplifies tool management and enhances extensibility.
2. History Compatibility: Implemented a robust unmarshaling logic that handles both old (genai.Content) and new (ai.Message) history formats, ensuring no data loss for existing users.
3. Bug Fixes: Resolved a compilation error in the httpBotter package that was present in the base branch.
4. Code Quality: Enhanced context key safety and performed repository cleanup.
5. Documentation: Significantly improved the README with detailed setup, environment variables, and API usage examples.

The solution has been verified through successful builds of the entire workspace and targeted testing of the history migration logic.

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PR created automatically by Jules for task 581450110787560854 started by @Gerifield

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