add submission created_at index

app/models/submission.rb

@@ -31,6 +31,7 @@
 #  index_submissions_on_account_id_and_id_pending                   (account_id,id) WHERE ((completed_at IS NULL) AND (archived_at IS NULL))
 #  index_submissions_on_account_id_and_template_id_and_id           (account_id,template_id,id) WHERE (archived_at IS NULL)
 #  index_submissions_on_account_id_and_template_id_and_id_archived  (account_id,template_id,id) WHERE (archived_at IS NOT NULL)
+#  index_submissions_on_created_at                                  (created_at)
 #  index_submissions_on_created_by_user_id                          (created_by_user_id)
 #  index_submissions_on_slug                                        (slug) UNIQUE
 #  index_submissions_on_template_id                                 (template_id)

db/migrate/20260707055354_add_submission_created_at_index.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class AddSubmissionCreatedAtIndex < ActiveRecord::Migration[8.1]
+  def change
+    add_index :submissions, :created_at, if_not_exists: true
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.1].define(version: 2026_07_01_165617) do
+ActiveRecord::Schema[8.1].define(version: 2026_07_07_055354) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "btree_gin"
   enable_extension "pg_catalog.plpgsql"
@@ -379,6 +379,7 @@ ActiveRecord::Schema[8.1].define(version: 2026_07_01_165617) do
     t.index ["account_id", "id"], name: "index_submissions_on_account_id_and_id_pending", where: "((completed_at IS NULL) AND (archived_at IS NULL))"
     t.index ["account_id", "template_id", "id"], name: "index_submissions_on_account_id_and_template_id_and_id", where: "(archived_at IS NULL)"
     t.index ["account_id", "template_id", "id"], name: "index_submissions_on_account_id_and_template_id_and_id_archived", where: "(archived_at IS NOT NULL)"
+    t.index ["created_at"], name: "index_submissions_on_created_at"
     t.index ["created_by_user_id"], name: "index_submissions_on_created_by_user_id"
     t.index ["slug"], name: "index_submissions_on_slug", unique: true
     t.index ["template_id"], name: "index_submissions_on_template_id"