Update UI to a burnt amber color theme

[horlorlahdeh]

Motivation

• Refresh the app look by switching the global theme to a warm burnt-amber palette for improved visual cohesion across the client UI.

Description

• Changed global CSS theme variables in client/src/App.css to set --primary-color, --dark-color, and --light-color to burnt-amber-friendly values.
• Adjusted base page background and default text color in client/src/App.css to harmonize with the new palette.
• No other files or application logic were modified.

Testing

• Running npm run build --prefix client failed in this environment under Node 22 due to an OpenSSL-related error (ERR_OSSL_EVP_UNSUPPORTED).
• Running NODE_OPTIONS=--openssl-legacy-provider npm run build --prefix client succeeded and produced a production build with warnings (Browserslist and an ESLint unused-variable warning).
• Starting the client in development with NODE_OPTIONS=--openssl-legacy-provider npm run client compiled the app (with the same warnings) and a screenshot of the updated landing page was captured for visual confirmation.

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Codex Task