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/device_store.py

@@ -48,8 +48,6 @@ class Device:
         self.rgbw = rgbw
         self.created_at = created_at or datetime.utcnow()
         self.updated_at = updated_at or datetime.utcnow()
-        # Preserved from old JSON for migration — not written back
-        self._legacy_calibration = None
 
     def to_dict(self) -> dict:
         """Convert device to dictionary."""
@@ -77,12 +75,8 @@ class Device:
 
     @classmethod
     def from_dict(cls, data: dict) -> "Device":
-        """Create device from dictionary.
-
-        Backward-compatible: reads legacy 'calibration' field and stores it
-        in _legacy_calibration for migration use only.
-        """
-        device = cls(
+        """Create device from dictionary."""
+        return cls(
             device_id=data["id"],
             name=data["name"],
             url=data["url"],
@@ -98,17 +92,6 @@ class Device:
             updated_at=datetime.fromisoformat(data.get("updated_at", datetime.utcnow().isoformat())),
         )
 
-        # Preserve old calibration for migration (never written back by to_dict)
-        calibration_data = data.get("calibration")
-        if calibration_data:
-            try:
-                from wled_controller.core.capture.calibration import calibration_from_dict
-                device._legacy_calibration = calibration_from_dict(calibration_data)
-            except Exception:
-                pass
-
-        return device
-
 
 class DeviceStore:
     """Persistent storage for WLED devices."""
@@ -196,6 +179,10 @@ class DeviceStore:
         """Create a new device."""
         device_id = f"device_{uuid.uuid4().hex[:8]}"
 
+        # Mock devices use their device ID as the URL authority
+        if device_type == "mock":
+            url = f"mock://{device_id}"
+
         device = Device(
             device_id=device_id,
             name=name,