Update timestamp type when changing sort

What does this MR do and why?

#515184 (closed)

In Migrate Your Work > Projects list to Vue and mo... (&13066 - closed) we are migrating Your work -> Projects to Vue with a GraphQL data source. Currently all projects show Updated at <timestamp> where timestamp is the updatedAt property. The Updated date sort for projects actually uses lastActivityAt property so there is a bit of a discrepancy in the timestamp that is displayed. This MR does two things:

• Use lastActivityAt instead of updatedAt for timestamp
• Default to Created at <timestamp> for sort items other than Updated date.

References

Please include cross links to any resources that are relevant to this MR. This will give reviewers and future readers helpful context to give an efficient review of the changes introduced.

• Migrate Your Work > Projects list to Vue and mo... (&13066 - closed)

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Before	After
Screen_Recording_2025-01-21_at_10.44.32_AM	Screen_Recording_2025-01-21_at_10.41.47_AM

How to set up and validate locally

1. Go to http://gdk.test:3000/rails/features and enable your_work_projects_vue feature flag
2. Go to http://gdk.test:3000/dashboard/projects
3. Change the sort from the dropdown