→ Camera scanning: Click "Start Camera Scanner" (grant permission)
→ File upload: Always available — click "Choose File" or drag & drop image below the preview area
Encode: Your input → Base64 → QR code
Scan result: Base64 string only (not original text)
Decode: Paste Base64 string → see original content
Scan: Read QR (camera or uploaded image) → auto-decode Base64 to original text