feat: HA value source test — raw value axis + behavior IconSelect

- WS sends raw_value and raw_range for HA entity streams
- Canvas draws right-side Y-axis labels: configured min/max range
  and current raw HA value (green, positioned at correct Y)
- Replace plain <select> for scene behavior with IconSelect (moon/sun)

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

@@ -384,7 +384,13 @@ async def test_value_source_ws(
     try:
         while True:
             value = stream.get_value()
-            await websocket.send_json({"value": round(value, 4)})
+            msg: dict = {"value": round(value, 4)}
+            if hasattr(stream, "get_raw_value"):
+                raw = stream.get_raw_value()
+                if raw is not None:
+                    msg["raw_value"] = round(raw, 4)
+                    msg["raw_range"] = [stream._min_ha, stream._max_ha]
+            await websocket.send_json(msg)
             await asyncio.sleep(0.05)
     except WebSocketDisconnect:
         logger.debug("Value source test WebSocket disconnected for %s", source_id)