fix: HA light target — brightness source, transition=0, dashboard type label

- Add brightness_value_source_id to HALightOutputTarget model, to_dict,
  from_dict, update_fields, register_with_manager, API response
- Wire value stream in HALightTargetProcessor: acquire/release on
  start/stop, multiply brightness in _update_lights loop
- Fix transition=0 not saving (parseFloat("0") || 0.5 was falsy)
- Fix dashboard showing "Key Colors" for HA targets — now "Home Assistant"
- Fix dashboard FPS showing 0/2 — HA targets show target/target
- Add CSS source subtitle to HA target dashboard cards

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

@@ -62,6 +62,7 @@ def _target_to_response(target) -> OutputTargetResponse:
             target_type=target.target_type,
             ha_source_id=target.ha_source_id,
             color_strip_source_id=target.color_strip_source_id,
+            brightness_value_source_id=target.brightness_value_source_id or "",
             ha_light_mappings=[
                 HALightMappingSchema(
                     entity_id=m.entity_id,