Present the last updated timestamp of a project

In order to have enough information to identify inactive projects, for example in the case of a deployment that supports an EDX course, the system should present the timestamp of the latest change in the project.

The latest change timestamp in a project corresponds to the last event timestamp recorded for the project (either the last project update event or the last resource event within the project).

Expected behavior:

- [ ] Delta should expose a new read-only project sub-resource (e.g. `last-updated` or `last-update-instant`) guarded by the same project read permission (`projects/read`)
- [ ] Fusion should display the last updated read-only information in the project details
- the value needs to be consistent, it cannot rely on the default views

Not in scope/to check:

- the CLI should show the last updated timestamp in DateTime and UNIX timestamp as a subcommand to the projects (e.g. `projects last-updated {org}/{proj} --format=unix-timestamp`)

Start by locating Delta's project read sub-resources and the Fusion project-details view. Trace how project and resource event timestamps are recorded, then verify the new read-only value uses the projects/read permission and remains consistent without relying on default views. Done means Delta exposes the timestamp and Fusion displays it; the CLI is explicitly out of scope.

Written by the indexing model from the issue text.