Preload SWF asset manifests during wardrobe item search

This doesn't matter a ton in production, where we already have most of
our manifests loaded! But it matters a lot on my relatively-fresh
development instance, at times like now when images.neopets.com is slow
to respond. A single item search was taking minutes before this change
(5 seconds of timeout per asset for 30 items!), but now takes a few
seconds the first time, as it should!

app/controllers/items_controller.rb

@@ -171,7 +171,13 @@ class ItemsController < ApplicationController
         appearance_params[:color_id], appearance_params[:species_id])
     end
 
-    target.appearances_for(@items.map(&:id), swf_asset_includes: [:zone])
+    target.appearances_for(@items.map(&:id), swf_asset_includes: [:zone]).
+      tap do |appearances|
+        # Preload the manifests for these SWF assets concurrently, rather than
+        # loading them in sequence when we generate the JSON.
+        swf_assets = appearances.values.map(&:swf_assets).flatten
+        SwfAsset.preload_manifests(swf_assets)
+      end
   end
   
   def search_error(e)