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/storage/picture_target.py

@@ -56,9 +56,8 @@ class PictureTarget:
     @classmethod
     def from_dict(cls, data: dict) -> "PictureTarget":
         """Create from dictionary, dispatching to the correct subclass."""
-        target_type = data.get("target_type", "wled")
-        # "wled" and "led" both map to WledPictureTarget (backward compat)
-        if target_type in ("wled", "led"):
+        target_type = data.get("target_type", "led")
+        if target_type == "led":
             from wled_controller.storage.wled_picture_target import WledPictureTarget
             return WledPictureTarget.from_dict(data)
         if target_type == "key_colors":