Don't dead-end users with out-of-date links to files

Summary: Ref T10262. Instead of dumping an unhelpful 403 "ACCESS DENIED" page on users, explain the most likely cause of the issue and give them a link to return to the file detail page to learn more or get an up-to-date link.

Test Plan: Hit both errors, had a lovely experience with the helpful dialog text.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10262

Differential Revision: https://secure.phabricator.com/D15650