Add deepseek-reasoner (R1) model

[boowangoo]

Description

Added the new Deepseek R1 model (model=deepseek-reasoner).
Model description derived from deepseek-reasoner documentation.

Checklist

• [] The relevant docs, if any, have been updated or created
• [] The relevant tests, if any, have been updated or created

Screenshots

Testing instructions

I tracked my usage on the DeepSeek website.

Initial usage:

Then I performed a single prompt (captured in "Screenshots") using the new model. Then I waited 10 minutes and refreshed the DeepSeek usage page.

After prompt:

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