Expression Details Page

Expression details should be listed on a page with a unique URL.
URL should include the Expression ID.
URL should optionally include a slug containing the expression's title, for better SEO.

Details page should list all relevant expression details, a link to a tester that will prefill the expression, and Like and Dislike buttons (that will trigger a login if the user isn't authenticated, when clicked).

The issue names no files, tests, or entry points. Start by locating the expression model, routing, and existing tester and authentication pages; done means a unique ID-based URL, optional title slug, complete expression details, a prefilled tester link, and authenticated Like/Dislike actions.

Written by the indexing model from the issue text.