Enhance the LLM Serving Pack with Default Metadata

[jbouder]

Summary

The Nebari LLM serving pack registers a card on the Nebari landing page via the landingPage block of its key-manager NebariApp resource (charts/nebari-llm-serving/values.yaml, rendered by templates/key-manager-nebariapp.yaml). Today that card reuses the generic built-in keycloak icon and leaves several recommended defaults (visibility, healthCheck) unset. This issue covers designing and shipping a dedicated LLM-themed icon and filling in the remaining landingPage defaults so the card matches the quality and behavior of other packs (e.g. nebari-chat-pack).

Motivation

• The card currently borrows the nebari icon, which misrepresents the service
• visibility is unset, so the card defaults to public; other packs/examples set authenticated for an authenticated-user UI
• healthCheck is unset, so the card's status stays unknown; peer packs configure a probe path so health is reported
• displayName: "LLM API Keys" and priority: 100 deserve a review for consistency with sibling packs
• A purpose-built, light/dark-aware icon gives the pack a polished, recognizable presence on the landing page

Acceptance Criteria

• A dedicated LLM-serving icon is designed as an .svg (light/dark variants if needed) and committed to the pack repo (e.g. under charts/nebari-llm-serving/assets/ or hosted at a stable URL)
• charts/nebari-llm-serving/values.yaml landingPage.icon references the new asset (custom URL) instead of the built-in keycloak key; landingPage.iconLight / landingPage.iconDark set if separate variants exist
• templates/key-manager-nebariapp.yaml renders the new icon/iconLight/iconDark fields correctly
• landingPage.visibility is set to an explicit, intentional value (e.g. authenticated)
• landingPage.healthCheck is configured (enabled: true + a valid path, e.g. /healthz) so the card reports real status
• landingPage.category, priority, displayName, and description reviewed and aligned with sibling packs (nebari-chat-pack)
• examples/argocd-application.yaml updated to mirror the new landingPage defaults
• Card verified end-to-end: correct icon (light + dark mode), title, category, and health status render on the landing page

Out of Scope

• Adding a second landing-page card for the LLM operator itself (only the key-manager UI has landing-page presence today)
• Changes to the landing-page rendering/icon-resolution logic in the nebari-landing repo (ServiceIcon.tsx, NebariApp schema) — this issue only sets values the existing schema already supports
• pack-metadata.yaml (the pack-dashboard identity), which is separate from the landing-page card
• Per-model LLMModel configuration and access control