Add a Black Forest Labs inference provider adapter [#3601119]

Problem/Motivation

Add a Black Forest Labs inference provider adapter to `ai_provider_huggingface`, so configured models can be served by Black Forest Labs. Part of the configurable Inference Provider routing effort (blocked by the base framework issue).

Steps to reproduce

Proposed resolution

HuggingFace Providers

Remaining tasks

User interface changes

API changes

Data model changes

Issue fork ai_provider_huggingface-3601119

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3601119-add-a-black changes, plain diff MR !24
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