feat: add build checks for app/client and landing page

[gelluisaac]

Description

This PR modifies the workflow to check for build errors in the app/client and landing page, in addition to the existing contract tests. The changes ensure that the CI/CD pipeline fails if any build errors occur, improving the reliability of the deployment process.

Changes

• Added a new job (build-client) to the GitHub Actions workflow.
• The build-client job:
  • Sets up Node.js and installs dependencies for app/client.
  • Builds the app/client using npm run build.
  • Builds the landing page using npm run build-landing-page.
• Updated the package.json to include the build-landing-page script.

Related Issues
Closes #

Type of Change

• 🐛 Bug fix or ⚙️ enhancement
• ✨ New feature or Chore (change with no new features or fixes)
• 📚 Documentation update

Testing

• Verified that the workflow runs successfully in GitHub Actions.
• Manually tested the app/client and landing page builds locally.
• Confirmed that the workflow fails if build errors are introduced.

[Solomonsolomonsolomon]

@gelluisaac any updates on the PR?

[gelluisaac]

working on it now sir