Add local Flux2 ComfyUI generator

[ernop]

Summary

• Add a LocalFlux2Uncensored generator backed by a local ComfyUI /prompt + /history workflow.
• Add setup tooling and docs under tools/local-flux2-comfy/ for local Flux2 Klein + uncensored text encoder workflows.
• Add direct first-party image-provider generator support for ByteDance Seedream, MiniMax Hailuo, Krea 2, BRIA FIBO, Magnific Mystic, Luma Photon, Runway Gen-4 Image, and Stability AI SD3.5.
• Add settings for all new direct endpoints, API keys, model/default size knobs, async polling timeout, and optional local Flux2 node overrides.
• Add REPL names: flux2local, seedream, hailuo, krea, bria, magnific, luma, runway, and stability.

Validation

• dotnet build MultiImageClient.sln -p:EnableWindowsTargeting=true
• bash -n tools/local-flux2-comfy/setup_local_flux2_comfyui.sh
• python3 -m json.tool "MultiImageClient/settings - Fill this in and rename it.json"

Notes

• The local setup script binds ComfyUI to localhost by default and requires explicit opt-in before downloading the gated uncensored text encoder.
• The local Flux2 generator refuses non-local ComfyUI endpoints unless LocalFlux2AllowRemoteEndpoint is set for a trusted LAN host.
• Direct-provider generators were build-validated but not live API-tested because provider credentials are not present in this environment.