New button next to Download PNG writes the rendered QR as a PNG Blob
to the system clipboard via the async Clipboard API, with a brief
in-button confirmation (Copied!) or error state.
The wget probe failed because nginx listens on IPv4 only while BusyBox
wget resolved localhost to ::1 first, returning Connection refused
despite a healthy nginx. A static SPA needs no liveness probe beyond
the container's running state; remove the HEALTHCHECK entirely.
Generates QR codes from a URL with center logo upload, adjustable logo
padding and size, dot/corner-square/corner-dot style pickers, color
controls, and PNG/SVG export. Uses error correction level H so the
logo can occlude up to ~30% of modules without breaking scannability.
