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>

src/lib/translations.ts

@@ -112,7 +112,6 @@ export const translations = {
         docs: 'Docs',
         blog: 'Blog',
         pricing: 'Pricing',
-        contact: 'Contact',
         launchApp: 'Launch App',
       },
       hero: {
@@ -162,17 +161,6 @@ export const translations = {
         proFeatures: ['Unlimited uploads', 'All export formats', 'Priority processing', 'API access'],
         enterpriseFeatures: ['Custom volume', 'Dedicated support', 'SLA guarantee', 'On-premise option'],
       },
-      contact: {
-        title: 'Contact Us',
-        subtitle: 'Get in touch with our team',
-        nameLabel: 'Name',
-        emailLabel: 'Email',
-        messageLabel: 'Message',
-        send: 'Send Message',
-        sending: 'Sending...',
-        sent: 'Message sent!',
-        qqGroup: 'QQ Group',
-      },
       footer: {
         tagline: 'AI-powered math formula recognition',
         product: 'Product',
@@ -294,7 +282,6 @@ export const translations = {
         docs: '文档',
         blog: '博客',
         pricing: '价格',
-        contact: '联系我们',
         launchApp: '启动应用',
       },
       hero: {
@@ -344,17 +331,6 @@ export const translations = {
         proFeatures: ['无限上传', '所有导出格式', '优先处理', 'API 访问'],
         enterpriseFeatures: ['自定义用量', '专属支持', 'SLA 保障', '私有部署选项'],
       },
-      contact: {
-        title: '联系我们',
-        subtitle: '与我们的团队取得联系',
-        nameLabel: '姓名',
-        emailLabel: '邮箱',
-        messageLabel: '留言',
-        send: '发送消息',
-        sending: '发送中...',
-        sent: '消息已发送！',
-        qqGroup: 'QQ 群',
-      },
       footer: {
         tagline: 'AI 驱动的数学公式识别',
         product: '产品',