Fix ESLint warnings for img elements

Add ESLint disable comments for @next/next/no-img-element warnings where appropriate (barcode images with base64 data URIs don't benefit from Next.js Image optimization) and add missing alt attribute to PDF417 barcode component.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

app/ui/Pdf417Barcode.tsx

@@ -23,6 +23,7 @@ export const Pdf417Barcode:FC<{hub3aText:string, className?: string}> = ({hub3aT
     }
 
     return (
-        <img src={bitmapData} className={className} style={className ? undefined : { width: "350px", height: "92px" }} />
+        // eslint-disable-next-line @next/next/no-img-element
+        <img src={bitmapData} alt="PDF417 Barcode" className={className} style={className ? undefined : { width: "350px", height: "92px" }} />
     );
 }