Add support for is_manually_nc

A really really simple change! It works on the item page, the item
index page, item search, the homepage, and the item lists page.

The main reason I avoided this for so long (even before modernizing the
Rails app) was that the ElasticSearch stuff felt like it made it messy?
But now it's pretty simple, and it works in search already cuz I did
that when I implemented item search, so, nice!

app/controllers/closet_hangers_controller.rb

@@ -260,7 +260,7 @@ class ClosetHangersController < ApplicationController
   end
 
   def items_scope
-    Item.select(:id, :thumbnail_url, :rarity_index)
+    Item.select(:id, :thumbnail_url, :rarity_index, :is_manually_nc)
   end
 
   def item_translations_scope

app/controllers/outfits_controller.rb

@@ -50,7 +50,8 @@ class OutfitsController < ApplicationController
     @colors = Color.funny.alphabetical
     @species = Species.alphabetical
     
-    newest_items = Item.newest.select([:id, :updated_at, :thumbnail_url, :rarity_index]).
+    newest_items = Item.newest.
+      select(:id, :updated_at, :thumbnail_url, :rarity_index, :is_manually_nc).
       includes(:translations).limit(18)
     @newest_modeled_items, @newest_unmodeled_items =
       newest_items.partition(&:predicted_fully_modeled?)

app/models/item.rb

@@ -169,7 +169,7 @@ class Item < ApplicationRecord
   end
 
   def nc?
-    NCRarities.include?(rarity_index)
+    is_manually_nc? || NCRarities.include?(rarity_index)
   end
   
   def pb?