note about whisper available devices

[przepeck]

🛠 Summary

adding note about available devices for whisper

🧪 Checklist

• Unit tests added.
• The documentation updated.
• Change follows security best practices.
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[Copilot]

Pull request overview

Adds a clarification note in the OpenWebUI integration demo about deploying Whisper models on different devices, to help users adjust audio transcription deployments.

Changes:

• Add a note indicating Whisper models (with an exception noted) may be deployed on CPU/NPU by changing the target device parameter.