feat: auto-scan receives 4 sequential ADC sets for multi-spectrum scan

Firmware does R→UV→Y→IR sequential scan autonomously. Miniprogram
now listens for 4 consecutive ADC notifications, storing each as a
separate spectrum group. Also listens for run_state=IDLE as scan
completion signal. Displays all 4 spectrum groups with PD1-PD7 bars.
Stores full scan data in globalData.lastScanData for diagnosis phase.

miniprogram/pages/auto-scan/auto-scan.wxss

@@ -121,6 +121,30 @@
   text-align: center;
 }
 
+.spectrum-group {
+  margin-bottom: 24rpx;
+}
+
+.spectrum-group:last-child {
+  margin-bottom: 0;
+}
+
+.spectrum-title {
+  font-size: 26rpx;
+  font-weight: 600;
+  color: #E6508C;
+  margin-bottom: 12rpx;
+  padding-bottom: 8rpx;
+  border-bottom: 2rpx solid #fdf2f8;
+}
+
+.empty-hint {
+  text-align: center;
+  color: #999;
+  font-size: 26rpx;
+  padding: 40rpx 0;
+}
+
 .scan-error {
   text-align: center;
   color: #ff4d4f;