Improve local Gradio launch defaults

[ivanalexsapozhnikov]

What changed

• Prefer the repository .venv when it already exists, even if another Conda or virtual environment is active.
• Keep the Gradio server local and open it in the user's browser instead of creating a public share URL.
• Leave the optional LoRA adapter unselected by default.

Why

The launcher could otherwise install or run dependencies in an unrelated active environment. The UI also exposed a public Gradio link by default and automatically applied the first discovered LoRA adapter, which made the initial result less predictable.

Validation

• bash -n launch_gradio.sh
• Python compilation of run/gradio_app.py
• Local Gradio startup and /config response verification