Simplify PushTarget by removing template method pattern

Each target now implements process directly with its own logic,
rather than using processable?/perform_push hooks. The pushable?
check is done once in Notification#push before iterating targets.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

saas/app/models/notification/push_target/native.rb

@@ -1,13 +1,11 @@
 class Notification::PushTarget::Native < Notification::PushTarget
-  private
-    def should_push?
-      super && devices.any?
-    end
-
-    def perform_push
+  def process
+    if devices.any?
       native_notification.deliver_later_to(devices)
     end
+  end
 
+  private
     def devices
       @devices ||= notification.identity.devices
     end

saas/test/models/notification/push_target/native_test.rb

@@ -50,16 +50,6 @@ class Notification::PushTarget::NativeTest < ActiveSupport::TestCase
     end
   end
 
-  test "does not push when creator is system user" do
-    stub_push_services
-    @identity.devices.create!(token: "test123", platform: "apple", name: "Test iPhone")
-    @notification.update!(creator: users(:system))
-
-    assert_no_native_push_delivery do
-      Notification::PushTarget::Native.new(@notification).process
-    end
-  end
-
   test "pushes to multiple devices" do
     stub_push_services
     @identity.devices.delete_all