plugins: add Local LLM Manager 0.4.0

[GbaGuy]

What is this?

Local LLM Manager, a bar widget: Pick a local model and start or stop it from the bar.

Checklist

• One folder under its catalogue with a manifest and a real preview image (not a placeholder).
• One entry added to that catalogue's registry.json (lastUpdated in YYYY-MM-DD; official: false for community items).
• Tested live in Ryoku, it renders and behaves correctly (installed with ryoku plugin add).
• tests/validate-catalogue.sh passes from the repo root.
• I own or have permission to submit this content, and it is licensed for redistribution.
• It does not overwrite user configuration or run privileged commands without clear consent.

Opened with ryoku plugin share; the product manifest and the registry entry were generated from the installed plugin.