Encapsulate target-type dispatch via polymorphism (Phase 1)

Replace isinstance checks with polymorphic methods on PictureTarget
hierarchy: register_with_manager, sync_with_manager, update_fields,
and has_picture_source property.

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

server/src/wled_controller/api/routes/picture_targets.py

@@ -191,25 +191,10 @@ async def create_target(
         )
 
         # Register in processor manager
-        if isinstance(target, WledPictureTarget) and target.device_id:
-            try:
-                manager.add_target(
-                    target_id=target.id,
-                    device_id=target.device_id,
-                    settings=target.settings,
-                    picture_source_id=target.picture_source_id,
-                )
-            except ValueError as e:
-                logger.warning(f"Could not register target {target.id} in processor manager: {e}")
-        elif isinstance(target, KeyColorsPictureTarget):
-            try:
-                manager.add_kc_target(
-                    target_id=target.id,
-                    picture_source_id=target.picture_source_id,
-                    settings=target.settings,
-                )
-            except ValueError as e:
-                logger.warning(f"Could not register KC target {target.id}: {e}")
+        try:
+            target.register_with_manager(manager)
+        except ValueError as e:
+            logger.warning(f"Could not register target {target.id} in processor manager: {e}")
 
         return _target_to_response(target)
 
@@ -279,14 +264,14 @@ async def update_target(
             description=data.description,
         )
 
-        # Sync processor manager (unified API handles both target types)
+        # Sync processor manager
         try:
-            if data.settings is not None or data.key_colors_settings is not None:
-                manager.update_target_settings(target_id, target.settings)
-            if data.picture_source_id is not None:
-                manager.update_target_source(target_id, target.picture_source_id)
-            if data.device_id is not None and isinstance(target, WledPictureTarget):
-                manager.update_target_device(target_id, target.device_id)
+            target.sync_with_manager(
+                manager,
+                settings_changed=data.settings is not None or data.key_colors_settings is not None,
+                source_changed=data.picture_source_id is not None,
+                device_changed=data.device_id is not None,
+            )
         except ValueError:
             pass