feat: implement professional typography system with curated font pairings

Typography Presets (research-backed pairings):
- clean: Manrope + Inter (minimal, modern)
- editorial: Playfair Display + Raleway (fashion, lifestyle)
- modern: Space Grotesk + Inter (tech, futuristic)
- classic: Cormorant Garamond + Source Serif 4 (luxury, elegant)
- friendly: Fraunces + Work Sans (playful, quirky)
- minimal: DM Sans + Source Serif 4 (design-forward)
- impulse: Raleway + Inter (wellness, beauty)

Type Scale & Line Heights:
- Major Third (1.25) ratio for mathematical harmony
- H1: line-height 1.1, letter-spacing -0.025em
- H2: line-height 1.15, letter-spacing -0.02em
- H3: line-height 1.2, letter-spacing -0.015em
- Body: line-height 1.5 (WCAG compliant)
- Small text: letter-spacing +0.01em for readability

Fluid Typography:
- Headings use clamp() for smooth mobile→desktop scaling
- Display: 36px→48px, XL: 30px→40px, LG: 24px→32px

Performance:
- Variable font loading where available (Inter, Manrope, etc.)
- Removed unused fonts (Libre Baskerville, Nunito, Source Sans)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

lib/simpleshop_theme_web/components/layouts/root.html.heex

@@ -10,7 +10,7 @@
     <link phx-track-static rel="stylesheet" href={~p"/assets/css/app.css"} />
     <link rel="preconnect" href="https://fonts.googleapis.com">
     <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
-    <link href="https://fonts.googleapis.com/css2?family=Fraunces:opsz,wght@9..144,400;9..144,500;9..144,600;9..144,700&family=Inter:wght@400;500;600;700&family=Libre+Baskerville:wght@400;700&family=Nunito:wght@400;600;700&family=Nunito+Sans:opsz,wght@6..12,300;6..12,400;6..12,500;6..12,600&family=Outfit:wght@300;400;500;600&family=Source+Sans+3:wght@400;500;600&family=Space+Grotesk:wght@400;500;600&display=swap" rel="stylesheet">
+    <link href="https://fonts.googleapis.com/css2?family=Cormorant+Garamond:wght@400;500;600&family=DM+Sans:opsz,wght@9..40,400..700&family=Fraunces:opsz,wght@9..144,400..700&family=Inter:wght@300..700&family=Manrope:wght@400..700&family=Outfit:wght@300..600&family=Playfair+Display:wght@400;500;700&family=Raleway:wght@300;400;500&family=Source+Serif+4:wght@400;600&family=Space+Grotesk:wght@400..600&family=Work+Sans:wght@300..600&display=swap" rel="stylesheet">
     <script defer phx-track-static type="text/javascript" src={~p"/assets/js/app.js"}>
     </script>
     <script>