fix: call listVideoInputDevices on reader instance, not static

ZXing.BrowserMultiFormatReader.listVideoInputDevices is an instance
method, not a static method. Call codeReader.listVideoInputDevices()
after creating the reader. Also wrap in try/catch with null fallback
so decodeFromVideoDevice picks the default camera if enumeration fails.

static/index.html

@@ -2613,20 +2613,25 @@
         // Create reader with 1D-only hints for fast, accurate scanning
         codeReader = new ZXing.BrowserMultiFormatReader(_barcodeHints(), _barcodeOptions());
 
+        // Pick the rear-facing camera (environment-facing on phones)
+        let deviceId = null;
+        try {
+          const devices = await codeReader.listVideoInputDevices();
+          if (devices && devices.length > 0) {
+            const rear = devices.find(d =>
+              d.label && /back|rear|environment/i.test(d.label)
+            );
+            deviceId = rear ? rear.deviceId : devices[0].deviceId;
+          }
+        } catch (e) {
+          // Fallback: pass null to let decodeFromVideoDevice pick default
+          console.warn('listVideoInputDevices failed, using default camera:', e);
+        }
+
         document.getElementById('cameraPlaceholder').style.display = 'none';
         video.style.display = 'block';
         scanningActive = true;
 
-        // Pick the rear-facing camera (environment-facing on phones)
-        const devices = await ZXing.BrowserMultiFormatReader.listVideoInputDevices();
-        let deviceId = null;
-        if (devices && devices.length > 0) {
-          const rear = devices.find(d =>
-            d.label && /back|rear|environment/i.test(d.label)
-          );
-          deviceId = rear ? rear.deviceId : devices[0].deviceId;
-        }
-
         setScanStatus('Point camera at a barcode', 'success');
 
         // decodeFromVideoDevice handles camera + scanning in one call