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/theme/presets.ex

@@ -103,14 +103,14 @@ defmodule SimpleshopTheme.Theme.Presets do
   }
 
   @descriptions %{
-    gallery: "Elegant & editorial",
-    studio: "Clean & professional",
-    boutique: "Warm & sophisticated",
-    bold: "High contrast, strong",
-    playful: "Fun & approachable",
-    minimal: "Light & airy",
-    night: "Dark & dramatic",
-    classic: "Traditional & refined"
+    gallery: "Editorial serif headlines",
+    studio: "Clean modern sans-serif",
+    boutique: "Elegant classic serif",
+    bold: "Tech-forward geometric",
+    playful: "Quirky variable font",
+    minimal: "Light refined pairing",
+    night: "Dark tech aesthetic",
+    classic: "Traditional luxury serif"
   }
 
   # Core keys used to match presets (excludes branding-specific settings)