#137 - UI: use the absolute path to support different hostnames

[elookpotts-nvidia]

Description

This updates the UI to use the absolute path for logs, spec, etc. instead of the fully-qualified path when displayed in iframes. By doing so, the browser uses the domain of the page and the UI can fully function regardless of the service_base_url, which may be another domain.

For deployments like our brev launchable, this means that the service_base_url can be http://quick-start.osmo but still use the brev secure link for the UI.

Issue #137

Testing

1. Built images from this branch and pushed them to a private registry
2. Deployed a brev instance
3. curl -O https://raw.githubusercontent.com/NVIDIA/OSMO/refs/heads/main/deployments/brev/setup.sh
4. Update the osmo install to use the newly-built private images
5. Add a brev secure link for port 8000
6. Visit the secure link
7. Run any workflow from the UI, observe logs, spec, etc for the workflow

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.