feat: HA light output targets — cast LED colors to Home Assistant lights

New output target type `ha_light` that sends averaged LED colors to HA
light entities via WebSocket service calls (light.turn_on/turn_off):

Backend:
- HARuntime.call_service(): fire-and-forget WS service calls
- HALightOutputTarget: data model with light mappings, update rate, transition
- HALightTargetProcessor: processing loop with delta detection, rate limiting
- ProcessorManager.add_ha_light_target(): registration
- API schemas/routes updated for ha_light target type

Frontend:
- HA Light Targets section in Targets tab tree nav
- Modal editor: HA source picker, CSS source picker, light entity mappings
- Target cards with start/stop/clone/edit actions
- i18n keys for all new UI strings

server/src/wled_controller/storage/output_target.py

@@ -21,14 +21,24 @@ class OutputTarget:
         """Register this target with the processor manager. Subclasses override."""
         pass
 
-    def sync_with_manager(self, manager, *, settings_changed: bool, source_changed: bool, device_changed: bool) -> None:
+    def sync_with_manager(
+        self, manager, *, settings_changed: bool, source_changed: bool, device_changed: bool
+    ) -> None:
         """Push changed fields to a running processor. Subclasses override."""
         pass
 
-    def update_fields(self, *, name=None, device_id=None, picture_source_id=None,
-                      settings=None, key_colors_settings=None, description=None,
-                      tags: Optional[List[str]] = None,
-                      **_kwargs) -> None:
+    def update_fields(
+        self,
+        *,
+        name=None,
+        device_id=None,
+        picture_source_id=None,
+        settings=None,
+        key_colors_settings=None,
+        description=None,
+        tags: Optional[List[str]] = None,
+        **_kwargs,
+    ) -> None:
         """Apply mutable field updates. Base handles common fields; subclasses handle type-specific ones."""
         if name is not None:
             self.name = name
@@ -60,8 +70,14 @@ class OutputTarget:
         target_type = data.get("target_type", "led")
         if target_type == "led":
             from wled_controller.storage.wled_output_target import WledOutputTarget
+
             return WledOutputTarget.from_dict(data)
         if target_type == "key_colors":
             from wled_controller.storage.key_colors_output_target import KeyColorsOutputTarget
+
             return KeyColorsOutputTarget.from_dict(data)
+        if target_type == "ha_light":
+            from wled_controller.storage.ha_light_output_target import HALightOutputTarget
+
+            return HALightOutputTarget.from_dict(data)
         raise ValueError(f"Unknown target type: {target_type}")