QR decoder / QR reader / scan QR from URL / QR code OCR / barcode reader / link extraction from QR. Reads QR codes out of any public image URL (PNG / JPG / GIF / BMP) and returns the decoded text strings. Multiple QR codes in a single image are returned as separate entries. Wraps qrserver.com's free public read-qr-code API (true DIY decode requires canvas, which Workers don't have natively). Returns an empty `codes` array plus a descriptive `note` if the image can't be fetched or no QR is found.