[WIP] Add agentic mode toggle for prompt input panel

[Copilot]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

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This section details on the original issue you should resolve

<issue_title>Agentic Generation Mode</issue_title>
<issue_description>Add a new "Agentic Mode" toggle for the prompt input panel.

In Agentic Mode first an LLM ist called, that analyses the promt. The agent decides how many images need to be generated and generates prompts for each. the agnt then starts the generation. the generated images are showsn in-chat as a mini-gallery.

add an option in the admin section to configure an agent llm using litellm.</issue_description>

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[Copilot]

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