Add screenshot documentation of webapp homepage

[Copilot]

This PR demonstrates the successful build and deployment of the Rain Orderbook webapp homepage. Following the repository's Nix-based development workflow, I built the required dependencies and captured a screenshot of the homepage to document the current UI state.

Build Process Completed

Successfully executed the full build chain required for the webapp:

1. Rust Dependencies: Built @rainlanguage/orderbook package from Rust crates
2. UI Components: Built @rainlanguage/ui-components package
3. Webapp: Built @rainlanguage/webapp package
4. Development Server: Started the webapp dev server on http://localhost:5173/

Homepage Screenshot

The screenshot shows the webapp homepage rendering correctly with all key components:

Features Visible:

• Header Navigation: Raindex logo with "Docs" and "Dashboard" navigation links
• Hero Section: Large "Trade onchain without limits" heading with prominent call-to-action buttons
• Feature Grid: Three-column layout showcasing core platform benefits:
  • Automated: Onchain automated trading orders
  • Trustless: Non-custodial architecture with competing solvers
  • Infinitely Flexible: Support for custom Rainlang orders and common strategies

The homepage successfully loads and displays the expected content layout, confirming the webapp build process and component rendering are working correctly.

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