🐋 ci: Dockerfile.multi rewrite, maintain package integrity

[danny-avila]

• Removed the prod-stage build in Dockerfile.multi, opting to share dist files between services instead.
• Implemented a new base stage in Dockerfile.multi to centralize common setup steps.
• Restructured the build stages to optimize caching and reduce redundant operations.
• Added a named volume 'client-dist' in deploy-compose.yml to share client dist files between services.
• Updated the NGINX configuration in deploy-compose.yml to use the shared client dist files.
• Removed the 'prepare' script from package.json as it's no longer needed in the new build process.
• Made minor adjustments to the server code, improving readability and organization.

While this may affect users employing usage of deploy-compose.yml, the changes are necessary as prior to these changes, the project's package versions are not maintained across builds.