RecipeForm assumes that the `recipes` source is enabled

Problem/Motivation

RecipeForm includes a hard-coded redirect back to /admin/modules/browse/recipes. This can lead to a 404 if the recipes source isn't enabled, but even if it is, it might not be the page you came from (if, say, you installed a recipe via a mini-browser on another page). It's from a year ago, when Project Browser looked quite different.

Proposed resolution

The form should redirect back to the page you were on, whose path should be passed to the activate route in a URL query parameter.

This will not need explicit coverage because the desired code path is already verified by the existing tests.