Add optional LLM cluster naming

[adsharma]

Summary

• add optional OpenRouter/OpenAI-compatible LLM config for cluster naming
• default to endpoint https://openrouter.ai and model deepseek-v4-flash
• keep graph loading local-only, then name only currently visible drill-view clusters on demand
• cap visible cluster naming requests to avoid excessive LLM traffic and log each phase without printing tokens
• collapse the sidebar Cluster Names config by default

Validation

• npm run build:frontend
• npm run lint
• cargo check
• cargo check --features icebug-analytics