Lower bcrypt cost in tests to speed up the suite (#27)

Set BCrypt::Engine.cost to the minimum in test_helper so fixtures and
has_secure_password digests stop hashing at the default cost (12). This
roughly halves the suite's CPU time and speeds up password-touching specs.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: kcdragon

test/test_helper.rb

@@ -1,4 +1,9 @@
 ENV["RAILS_ENV"] ||= "test"
+
+# Hash passwords at bcrypt's minimum cost in tests to improve test speed.
+require "bcrypt"
+BCrypt::Engine.cost = BCrypt::Engine::MIN_COST
+
 require_relative "../config/environment"
 require "rails/test_help"
 require_relative "test_helpers/session_test_helper"