fix: update outdated HOME_URL in /etc/os-release

Closes #4329

Changes

• Added a RUN command in the Dockerfile runtime stage to update the HOME_URL in /etc/os-release
• Changes the outdated link from https://github.com/HeyPuter/phoenix (404) to https://github.com/HeyPuter/puter
• The fix is conditional - only runs if /etc/os-release exists

Testing

• The change is a simple sed replacement in the Dockerfile
• No functional changes to the application
• Only affects the metadata in the container's os-release file

Context

The issue reported that the container's /etc/os-release file contains an outdated GitHub link pointing to https://github.com/HeyPuter/phoenix which returns 404. This fix updates the link to point to the main Puter repository.