fix: hide loading indicator after SensorChart renders

The SensorChart hook was creating charts successfully but never removing
the loading overlay, causing charts to appear stuck on 'Loading chart...'.

Now removes the [data-loading] element after the chart is created.

assets/js/app.ts

@@ -357,6 +357,12 @@ const SensorChart: SensorChartHook = {
         }
       }
     })
+
+    // Hide loading indicator after chart is created
+    const loadingEl = this.el.querySelector('[data-loading]')
+    if (loadingEl) {
+      loadingEl.remove()
+    }
   },
 
   handleLiveDataUpdate(event: any) {