Design & Add a Dedicated Landing-Page Icon for the LLM Model Serving Pack

[jbouder]

Summary

The pack renders an "LLM API Keys" card on the Nebari landing page via the nebariapp.landingPage block (deployed through the ArgoCD Application. The block sets displayName, description, category: Security, priority, and healthCheck but no icon, so the card uses the generic Nebari fallback logo. This issue covers designing a key manager-themed icon and wiring it in.

Motivation

• The card currently shows the generic Nebari fallback logo with no service-specific identity
• A distinct icon helps users distinguish a service at a glance
• Keeps the pack visually consistent with other packs receiving dedicated icons
• Low-risk, additive change — landingPage.icon is already an accepted field

Acceptance Criteria

• A key manager-themed icon is designed as an .svg (with light/dark variants if needed) and committed to the nebari-llm-serving-pack chart repo, or published at a stable URL
• The chart's values.yaml exposes nebariapp.landingPage.icon (and iconLight/iconDark if used) and the chart template renders it into the NebariApp
• The ArgoCD Application override in apps/apps/llm-serving-pack.yaml sets landingPage.icon to the new asset
• A new chart targetRevision is published containing the icon support/value, and the ArgoCD app pins to it
• Card verified on the landing page in both light and dark mode

Out of Scope

• Changes to landing-page rendering / icon-resolution logic in the nebari-landing repo
• Re-tuning other landingPage defaults (category, priority, description, healthCheck) — already set
• Application/web-UI iconography unrelated to the landing-page card