dashboard: light/dark mode toggle (warm parchment + deep amber)

[AlexCheema]

Summary

Adds a light/dark mode toggle to the EXO dashboard with an original "Mission Control, Dawn Shift" aesthetic.

Light mode palette — warm parchment + deep amber/brass:

• Background: oklch(0.97 0.015 80) — warm near-white, like aged paper
• Cards: oklch(0.92 0.012 80) — aged cream
• Borders: oklch(0.83 0.009 78) — warm taupe
• Accent: oklch(0.50 0.14 65) — deep amber/brass (readable on light)
• Foreground: oklch(0.13 0.015 75) — warm near-black

Dark mode unchanged — same command-center blacks and bright yellow.

Implementation

• theme.svelte.ts — 28-line Svelte 5 rune store, no mode-watcher dependency
• FOUC prevention: html starts as class="dark", inline script reads localStorage and switches before first paint
• html.light CSS class approach (not :not(.dark)) for explicit, clean overrides
• Sun/moon icon toggle in the HeaderNav right section
• Persists to localStorage under key exo-theme

Files changed

• dashboard/src/lib/stores/theme.svelte.ts (new)
• dashboard/src/app.html
• dashboard/src/routes/+layout.svelte
• dashboard/src/lib/components/HeaderNav.svelte
• dashboard/src/app.css

Test plan

• Toggle button switches between sun (dark mode) and moon (light mode) icons
• All major pages (topology, chat, downloads) render correctly in light mode
• Theme persists across page reloads
• No flash of wrong theme on load (FOUC prevention working)
• Dark mode visually unchanged

🤖 Generated with Claude Code

[AlexCheema]

Screenshots

Dark mode — command center aesthetic (unchanged):

Light mode — "Mission Control, Dawn Shift" (warm parchment + deep amber):

Toggle is in the top-right nav (sun icon = currently dark → switch to light; moon icon = currently light → switch to dark). Theme persists via localStorage.