feat: adopt Tailwind CSS utility classes for styling

[nicomiguelino]

Summary

Migrates menu-board-app to Tailwind CSS utility classes, part of the company-wide rollout across edge-app repos. Reference pilot implementations: Screenly/clock-app#12 and Screenly/weather-app#6.

• index.html: replaced custom CSS classes with Tailwind utility classes using arbitrary-value bracket syntax for exact px/rem/gradient/shadow/color values (e.g. text-[3.5rem], bg-[linear-gradient(...)], shadow-[...], max-[1200px]: for the app's custom max-width breakpoints).
• src/main.ts: the dynamically rendered menu item cards (renderPage()) now carry Tailwind utility classes appended to their existing class names. Named CSS grid areas (grid-template-areas) are expressed via Tailwind's arbitrary-property bracket syntax directly on the elements.
• src/css/style.css: slimmed to the standard layered import (@layer theme, base, utilities + tailwindcss/theme.css + @screenly/edge-apps/styles + tailwindcss/utilities.css), plus the two custom @font-face rules (Playfair Display, Source Sans 3) and a handful of things that genuinely can't be static utilities:
  • .fade-out { opacity: 0 } — toggled at runtime via classList.add/remove('fade-out').
  • .label.vegetarian/.spicy/.gluten-free color overrides — keyed off arbitrary, user-configured label text lower-cased at render time, so they can't be resolved into the template ahead of time.
  • The @supports not (backdrop-filter: blur(10px)) fallback.
  • :root custom properties --accent-color (overridden at runtime via documentElement.style.setProperty) and --spacing-md (read by main.ts for the header's fallback margin), still referenced from Tailwind arbitrary values (text-[var(--accent-color)], etc.).
• package.json: bumped @screenly/edge-apps to ^1.3.0 (unpublished; ships Tailwind support). Lockfile untouched.
• Regenerated all screenshots/*.webp.

This repo did not previously import @screenly/edge-apps/styles (it had its own bespoke reset/tokens) — it's now brought in line with the rest of the fleet via the standard layered CSS entry point, same as the two pilot repos.

Test plan

• bun run type-check — passes
• bun test src/ — 14/14 pass
• bun run build — builds cleanly (only pre-existing, unrelated import.meta/chunk-size warnings)
• bun run screenshots — all 10 resolutions generated successfully
• Visually compared several new screenshots (1920x1080, 1080x1920 portrait, 800x480) against the previous versions — pixel-identical layout, including a pre-existing logo/card overlap quirk at very short viewport heights that predates this change.