feat: replace all marketing home components with reference landing design

- Extract landing.css (scoped under .marketing-page) from texpixel-landing.html
- Add Lora + JetBrains Mono fonts to index.html
- Update MarketingLayout with .marketing-page wrapper and glow blobs
- Replace MarketingNavbar with reference design (auth-aware user menu)
- Replace HeroSection with mock window + cycling LaTeX typing effect
- Replace FeaturesSection, PricingSection, Footer with reference designs
- Add ProductSuiteSection, ShowcaseSection, TestimonialsSection (carousel), DocsSeoSection
- Add useScrollReveal hook for intersection-based fade-in animations
- Update HomePage to wire all sections in correct order
- Remove obsolete HowItWorksSection and ContactSection
- Remove dead contact key from marketing.nav translations

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

index.html

@@ -12,7 +12,7 @@
   <!-- Fonts: Plus Jakarta Sans (headings) + DM Sans (body) -->
   <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=Plus+Jakarta+Sans:wght@500;600;700;800&family=DM+Sans:ital,wght@0,400;0,500;0,600;1,400&display=swap" rel="stylesheet" />
+  <link href="https://fonts.googleapis.com/css2?family=Plus+Jakarta+Sans:wght@500;600;700;800&family=DM+Sans:ital,opsz,wght@0,9..40,300;0,9..40,400;0,9..40,500;0,9..40,600;1,9..40,300&family=Lora:ital,wght@0,400;0,600;0,700;1,400&family=JetBrains+Mono:wght@400;500&display=swap" rel="stylesheet" />
 
   <!-- hreflang: same URL serves both languages (SPA), point both to canonical -->
   <link rel="canonical" href="https://texpixel.com/" />