@dicebear/converter vulnerable to ncontrolled memory allocation via crafted SVG dimensions

DiceBear is an avatar library for designers and developers. Prior to version 9.4.0, the `ensureSize()` function in `@dicebear/converter` read the `width` and `height` attributes from the input SVG to determine the output canvas size for rasterization (PNG, JPEG, WebP, AVIF). An attacker who can supply a crafted SVG with extremely large dimensions (e.g. `width="999999999"`) could force the server to allocate excessive memory, leading to denial of service. This primarily affects server-side applications that pass untrusted or user-supplied SVGs to the converter's `toPng()`, `toJpeg()`, `toWebp()`, or `toAvif()` functions. Applications that only convert self-generated DiceBear avatars are not practically exploitable, but are still recommended to upgrade. This is fixed in version 9.4.0. The `ensureSize()` function no longer reads SVG attributes to determine output size. Instead, a new `size` option (default: 512, max: 2048) controls the output dimensions. Invalid values (NaN, negative, zero, Infinity) fall back to the default. If upgrading is not immediately possible, validate and sanitize the `width` and `height` attributes of any untrusted SVG input before passing it to the converter.