Builds a complete favicon pack: PNG icons at 16, 32, 48, 64, 180 (Apple touch), 192 and 512 px, a multi-size favicon.ico, a site.webmanifest and the <link> tags to paste into <head>, all packaged as a ZIP written in the Worker. Upload an image (centre-cropped to a square) or leave the file empty to render a text favicon: an SVG with your initials on a rounded square, which browsers also rasterise into the PNG sizes. Everything runs locally.