feat: BindableFloat — universal value source binding for all scalar properties

Introduce BindableFloat abstraction that allows any numeric property to be
either a static value or dynamically driven by a ValueSource. Backward-compatible
serialization: plain float when unbound, {value, source_id} dict when bound.

Backend:
- storage/bindable.py — BindableFloat dataclass + bfloat() helper
- 25+ scalar properties converted across all entity types
- Runtime VS acquisition in ColorStripStreamManager for CSS bindings
- All stream hot loops use self.resolve() for live values
- KeyColorsColorStripStream now inherits ColorStripStream

Frontend:
- BindableScalarWidget (slider + VS picker toggle) for all editors
- TypeScript BindableFloat type + helpers
- Graph editor edges for all bindable properties
- Audio source channel IconSelect grid

Fixes: daylight longitude, candlelight wind_strength/candle_type from_dict

custom_components/wled_screen_controller/select.py

@@ -141,7 +141,12 @@ class BrightnessSourceSelect(CoordinatorEntity, SelectEntity):
         target_data = self.coordinator.data.get("targets", {}).get(self._target_id)
         if not target_data:
             return None
-        current_id = target_data["info"].get("brightness_value_source_id", "")
+        # BindableFloat: brightness is either a plain float or {"value": float, "source_id": str}
+        brightness = target_data["info"].get("brightness", "")
+        if isinstance(brightness, dict):
+            current_id = brightness.get("source_id", "")
+        else:
+            current_id = target_data["info"].get("brightness_value_source_id", "")
         if not current_id:
             return NONE_OPTION
         sources = self.coordinator.data.get("value_sources") or []
@@ -167,4 +172,7 @@ class BrightnessSourceSelect(CoordinatorEntity, SelectEntity):
             if source_id is None:
                 _LOGGER.error("Value source not found: %s", option)
                 return
-        await self.coordinator.update_target(self._target_id, brightness_value_source_id=source_id)
+        await self.coordinator.update_target(
+            self._target_id,
+            brightness={"value": 1.0, "source_id": source_id} if source_id else 1.0,
+        )