feat: revamp sensor add flow

assets/konva/app.js

@@ -377,6 +377,7 @@ function renderSensors() {
       if (!existing.isDragging()) existing.position({ x: absX, y: absY });
       existing.draggable(mode === 'sensorMove');
       existing.findOne('Text')?.text(label);
+      existing.findOne('.sensor-dot')?.fill(sensor.confirmed ? '#1565C0' : '#9E9E9E');
       return;
     }
 
@@ -394,8 +395,9 @@ function _buildSensorGroup(sensor, absX, absY, label) {
 
   // Visible dot — hitFunc expands the touch target without changing appearance.
   group.add(new Konva.Circle({
+    name: 'sensor-dot',
     radius: 8,
-    fill: '#1565C0',
+    fill: sensor.confirmed ? '#1565C0' : '#9E9E9E',
     stroke: '#ffffff',
     strokeWidth: 2,
     hitFunc(ctx, shape) {