Design & Add a Dedicated Landing-Page Icon for the Nebari Chat Pack

Summary

The Nebari chat pack renders a "Chat" card on the Nebari landing page via the landingPage block in helm/nebari-chat/values.yaml. That block sets displayName, description, category, priority, and healthCheck but leaves icon unset, so the card falls back to the generic Nebari logo. This issue covers designing a chat-specific icon and wiring it into the chart.

Motivation

• The card currently shows the generic Nebari fallback logo, making it visually indistinguishable from other un-iconed services
• The chart already supports the field — helm/nebari-chat/templates/_helpers.tpl renders icon and values.schema.json permits it — only the asset and value are missing
• A recognizable chat/AI icon improves scannability of the landing page as more packs are added
• Brings the chat pack in line with packs that will ship dedicated icons

Acceptance Criteria

• A chat-themed icon is designed as an .svg (with light/dark variants if the glyph needs them) and committed to the chart (e.g. helm/nebari-chat/assets/) or published at a stable URL
• helm/nebari-chat/values.yaml sets landingPage.icon (and iconLight/iconDark if separate variants exist) to reference the new asset
• helm/nebari-chat/templates/_helpers.tpl renders the chosen icon field(s) correctly
• helm/nebari-chat/values.schema.json allows the icon field(s) used
• helm template output shows the icon value in the rendered NebariApp
• 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 (displayName, category, priority, healthCheck) — they are already set
• Application UI/in-app iconography unrelated to the landing-page card

Review helm/nebari-chat/values.yaml, templates/_helpers.tpl, and values.schema.json to confirm how landingPage icon fields are represented, then inspect the rendered NebariApp with helm template. Design and add the SVG asset, wire its value into the chart, and verify the card in nebari-landing in both light and dark mode.