feat: add support for Black Forest Labs Flux 2 Dev AI model

[Aulos]

Add type definitions for @cf/black-forest-labs/flux-2-dev model.

I am not sure why but this model is still not added to the available model list. The partnership was announced a month ago and it is in the docs.

It would be nice to have a better defined input, but the docs are quite lacking, so I assumed it handles same type as Request['body'], so ReadableStream<Uint8Array>.

Changes

• Input interface with multipart request support
• Output interface for Base64 image generation
• Base class implementation
• Model registration in AiModels interface

[github-actions]

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