feat: Add CalendarSync landing page with compelling value proposition

[AlecKriebel]

Summary

• Built a complete landing page at the root route for CalendarSync with:
  • Hero section with tagline: "Sync Google Calendar to Spreadsheets Automatically"
  • Use Cases section covering time tracking, project billing, event reporting, and attendance logging
  • How It Works section with 3 simple steps for onboarding
  • Pricing teaser with Free and Pro plans ($0 and $9/month)
  • CTA section to drive sign-ups with "Get Started Free"
• Updated site config with CalendarSync branding and SEO description
• Added SEO metadata with target keywords: calendar to spreadsheet, google calendar export automation

Test plan

• Verify landing page renders correctly at root route /
• Check all sections are visible: Hero, Use Cases, How It Works, Pricing, CTA
• Verify "Get Started Free" and "Start Free Trial" buttons link to /register
• Verify "See How It Works" button scrolls to the How It Works section
• Test responsive layout on mobile and desktop
• Verify SEO metadata is present in page source

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