Add HAOS scene preset buttons and smooth tutorial scrolling

Expose scene presets as button entities in the HA integration under a
dedicated "Scenes" device. Each button activates its scene via the API.
The coordinator now fetches scene presets alongside other data, and the
integration reloads when the scene list changes.

Also animate tutorial autoscroll with smooth behavior and wait for
scrollend before positioning the spotlight overlay.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

custom_components/wled_screen_controller/strings.json

@@ -26,6 +26,11 @@
     }
   },
   "entity": {
+    "button": {
+      "activate_scene": {
+        "name": "{scene_name}"
+      }
+    },
     "switch": {
       "processing": {
         "name": "Processing"