Remove all migration logic, scroll tutorial targets into view, mock URL uses device ID

- Remove legacy migration code: profiles→automations key fallbacks, segments array
  fallback, standby_interval compat, profile_id compat, wled→led type mapping,
  legacy calibration field, audio CSS migration, default template migration,
  loadTargets alias, wled sub-tab mapping
- Scroll tutorial step targets into view when off-screen
- Mock device URL changed from mock://{led_count} to mock://{device_id},
  hide mock URL badge on device cards

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

server/src/wled_controller/main.py

@@ -57,11 +57,6 @@ value_source_store = ValueSourceStore(config.storage.value_sources_file)
 automation_store = AutomationStore(config.storage.automations_file)
 scene_preset_store = ScenePresetStore(config.storage.scene_presets_file)
 
-# Migrate embedded audio config from CSS entities to audio sources
-audio_source_store.migrate_from_css(color_strip_store)
-# Assign default audio template to multichannel sources that have none
-audio_source_store.migrate_add_default_template(audio_template_store)
-
 processor_manager = ProcessorManager(
     picture_source_store=picture_source_store,
     capture_template_store=template_store,