For remote notices, redirect to the original instead of 404.

We shouldn't treat these like local statuses, but I don't think a 404
is the right choice either here, because within pleroma-fe, these are
valid URLs. So with remote notices you have the awkward situation
where clicking a link will behave differently depending on whether you
open it in a new tab or not; the new tab will 404 if it hits static-fe.

This new redirecting behavior should improve that situation.

lib/pleroma/web/static_fe/static_fe_controller.ex

@@ -77,6 +77,11 @@ defmodule Pleroma.Web.StaticFE.StaticFEController do
 
       render(conn, "conversation.html", %{activities: timeline, meta: meta})
     else
+      %Activity{object: %Object{data: data}} ->
+        conn
+        |> put_status(:found)
+        |> redirect(external: data["url"] || data["external_url"] || data["id"])
+
       _ ->
         conn
         |> put_status(404)