feat: add environment configuration and update documentation

[thatbeautifuldream]

Summary

• Add .env.example file with environment configuration template
• Update .gitignore to include .env.example in version control
• Update README with environment configuration instructions for v0 integration

Changes

• Added: .env.example with NEXT_PUBLIC_BASE_URL configuration
• Modified: .gitignore to exclude .env* files but include .env.example
• Modified: README.md with new "Environment Configuration" section explaining how to set up the deployment URL for the "Open in v0" feature

[vercel]

@thatbeautifuldream is attempting to deploy a commit to the shadcn-pro Team on Vercel.

A member of the Team first needs to authorize it.