Fix bug sorting pet styles by creation date

Before this change, the sort order when searching for
"Prismatic Pine: Nostalgic" showed:

- [Added Dec 18, 2024] Prismatic Pine: Nostalgic Christmas Flotsam
- [Added Dec 19, 2024] Prismatic Pine: Nostalgic Christmas Gelert
- [Added Dec 18, 2024] Prismatic Pine: Nostalgic Christmas Bruce
- [Added Dec 17, 2024] Prismatic Pine: Nostalgic Christmas Scorchio
- <more>

This is because the Gelert was created at 11:37 NST on Dec 19, whereas
the Flotsam was created at 18:11 NST on Dec 18—but in UTC, which is how
timestamps are stored in the database, these are both Dec 19, so the
Flotsam was sorting first alphabetically.

In this change, we do a hacky transform from UTC to NST-ish. I didn't
want to set up the deploy process to pull named time zones into MySQL,
and then have this as a potential gotcha for the dev environment
later—so instead, I pretend `-08:00` is a good-enough specification of
NST.

This will sometimes create slightly incorrect sort ordering when it
*is* Daylight Savings, and a record was created around midnight. I'm
okay with that!

app/models/alt_style.rb

@@ -20,7 +20,11 @@ class AltStyle < ApplicationRecord
     where(series_name:, color_id: color.id, species_id: species.id)
   }
   scope :by_creation_date, -> {
-    order("DATE(created_at) DESC")
+    # HACK: Setting up named time zones in MySQL takes effort, so we assume
+    #       it's not Daylight Savings. This will produce slightly incorrect
+    #       sorting when it *is* Daylight Savings, and records happen to be
+    #       created around midnight.
+    order(Arel.sql("DATE(CONVERT_TZ(created_at, '+00:00', '-08:00')) DESC"))
   }
   scope :unlabeled, -> { where(series_name: nil) }
   scope :newest, -> { order(created_at: :desc) }