Fix account destroy cascade gaps

Account incineration could leave orphaned records due to missing cascade
declarations and async jobs failing when the account was already gone.

Cascade fixes:
- Add Account::Searchable concern to clean up Search::Query (delete_all)
  and Search::Record (destroy_all, respects SQLite FTS dependent: :destroy)
- Add before_destroy in Account::Storage to delete storage entries
- Suppress storage entry recording during incineration so attachment
  purge callbacks don't create entries or enqueue materialize jobs
- Guard Access#clean_inaccessible_data_later with unless user.destroyed?
  to avoid enqueuing pointless jobs during user cascade

Job tenancy:
- Extract AccountTenanted concern from the global ActiveJob initializer
  into ApplicationJob (include) with targeted prepends for
  ActionMailer::MailDeliveryJob and Turbo broadcast jobs
- Defer account resolution from deserialize to perform so that missing
  accounts raise DeserializationError inside the execution path where
  discard_on can handle it

Tests:
- Comprehensive incineration test covering 35 model types with
  before/after assertions and full enqueued job processing
- Mailer deliver_later test verifying account context survives job
  serialization for multi-account users
- Turbo broadcast test verifying account-scoped URLs in rendered partials

test/mailers/notification/bundle_mailer_test.rb

@@ -106,6 +106,19 @@ class Notification::BundleMailerTest < ActionMailer::TestCase
       "Should not generate a real email when all notifications are stale"
   end
 
+  test "deliver_later works with account context" do
+    # Give user a second account so the mailer includes the account name in the subject
+    second_account = Account.create!(name: "Second account")
+    second_account.users.create!(identity: @user.identity, role: :member, name: @user.name)
+
+    create_notification(@user)
+
+    Notification::BundleMailer.notification(@bundle).deliver_later
+    perform_enqueued_jobs
+
+    assert_emails 1
+  end
+
   private
     def create_notification(user, source: events(:logo_published))
       Notification.create!(user: user, creator: user, source: source, created_at: 30.minutes.ago)