Configure the application's default time zone to NST (US Pacific)

This doesn't affect a lot right now, it was previously defaulting to
UTC I think? And I've confirmed that, while timestamps are stored in
the database as UTC, they're not interpreted any differently with this
setting. (Or, rather, it's loaded as a `DateTime` object for the same
moment in time, but in the NST time zone. Good!)

But this feels like a more useful default for displaying things for
development etc, and moreover, I'm working on some logic for things
like "when do limited-time Dyeworks items expire exactly?", and that
logic is made *much* simpler if we can just compare dates in NST by
default rather than fudge around with the zones on them and figuring
out the correct midnight!

(Although, as I type this, I think I maybe have thought of an easier
way to do it? So maybe this change won't actually be necessary for
that, but it still feels like a more sensible default for us
regardless!)

config/application.rb

@@ -44,7 +44,7 @@ module OpenneoImpressItems
     # These settings can be overridden in specific environments using the files
     # in config/environments, which are processed later.
     #
-    # config.time_zone = "Central Time (US & Canada)"
+    config.time_zone = "Pacific Time (US & Canada)"
     # config.eager_load_paths << Rails.root.join("extras")
 
     config.i18n.fallbacks = true