ai tags: add buttons for quickly adding and removing tags on the /ai_tags page.

Add "Add" and "Remove" buttons beneath thumbnails on the /ai_tags page.
These let you add the tag to the post if it's correct, or remove it if
it's wrong.

app/policies/ai_tag_policy.rb

@@ -4,4 +4,8 @@ class AITagPolicy < ApplicationPolicy
   def index?
     true
   end
+
+  def tag?
+    unbanned? && record.post.present? && policy(record.post).update?
+  end
 end