feat: add demo mode to skip backend health check for GitHub Pages

[NotYuSheng]

• Add VITE_DEMO_MODE env variable to bypass backend health check
• Enable demo mode in GitHub Pages workflow build step
• Document the option in example.env

This allows the frontend to load on GitHub Pages without waiting for a backend that doesn't exist.

[gemini-code-assist]

Summary of Changes

Hello @NotYuSheng, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a "demo mode" feature that allows the frontend application to operate without an active backend connection. This is particularly useful for static deployments like GitHub Pages, where a backend might not be available. By setting an environment variable, the application can skip the usual backend health checks, ensuring the frontend loads successfully in such environments.

Highlights

• New Environment Variable: Introduced VITE_DEMO_MODE to control the backend health check behavior, primarily for static deployments.
• Conditional Backend Health Check: The useBackendHealth hook now bypasses the backend health check if VITE_DEMO_MODE is set to true.
• Documentation Update: The example.env file has been updated to include documentation for the new VITE_DEMO_MODE variable.
• GitHub Pages Integration: This feature is intended to enable the frontend to load on GitHub Pages without requiring a backend, by activating demo mode during the build process.

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Ignored Files

• Ignored by pattern: .github/workflows/** (1)
  • .github/workflows/deploy-gh-pages.yml

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[gemini-code-assist]

Code Review

This pull request introduces a 'demo mode' to allow the frontend to run without a backend, which is useful for deployments like GitHub Pages. The implementation correctly uses a Vite environment variable to bypass the backend health check. However, the current approach is incomplete as it doesn't handle other API calls, which will fail and break the user experience in demo mode. I've left a comment with a suggestion to improve this by mocking API responses.