fix: barcode scanner — hints not applied, per-frame errors killing scanner

Root cause #1: BrowserMultiFormatReader constructor takes 0 args so hints
and timing options (passed as args) were silently ignored. Hints are now
applied as reader.reader.hints, and timing as instance properties.

Root cause #2: ZXing per-frame 'no barcode' exceptions have message=undefined
causing .toLowerCase() to crash in old message-text filter. Switched to
instanceof checks against NotFoundException, ChecksumException, FormatException
which properly distinguishes normal 'no barcode' frames from real errors.

Tested in browser — hint setting and error filtering both verified working.

static/index.html

@@ -2885,7 +2885,12 @@
         if (!video) return;
 
         // Create reader with 1D-only hints for fast, accurate scanning
-        codeReader = new ZXing.BrowserMultiFormatReader(_barcodeHints(), _barcodeOptions());
+        // NOTE: BrowserMultiFormatReader constructor takes 0 args — hints and options
+        // must be set as instance properties for them to take effect.
+        codeReader = new ZXing.BrowserMultiFormatReader();
+        codeReader.reader.hints = _barcodeHints();
+        codeReader.timeBetweenScansMillis = 2000;  // delayBetweenScanSuccess
+        codeReader._timeBetweenDecodingAttempts = 300; // delayBetweenScanAttempts
 
         // Pick the rear-facing camera (environment-facing on phones)
         let deviceId = null;
@@ -2927,8 +2932,13 @@
               handleBarcode(val.trim());
             }
           } else if (err && scanningActive) {
-            const msg = (err.message || err || '').toLowerCase();
-            if (!msg.includes('multiformat') && !msg.includes('unable to detect')) {
+            // NotFoundException, ChecksumException, FormatException are normal
+            // "no barcode on this frame" results — silently continue scanning.
+            // We use instanceof because ZXing's minified exception classes all
+            // have message="undefined", making message-text filtering unreliable.
+            if (!(err instanceof ZXing.NotFoundException ||
+                  err instanceof ZXing.ChecksumException ||
+                  err instanceof ZXing.FormatException)) {
               console.error('ZXing camera error:', err);
               handleCameraError(new Error(err.message || err));
             }