feat: add AVIF output format support across 6 remaining tools (#85)

Closes #73

AVIF was already supported in the core engine, convert, compress,
optimize-for-web, upscale, erase-object, svg-to-raster, and
pdf-to-image tools. This adds AVIF as an output format option to
the 6 tools that were missing it: split, collage, stitch,
image-to-base64, noise-removal, and red-eye-removal.

For each tool, both the frontend format selector (with quality
slider for AVIF's lossy encoding) and the backend Zod schema +
Sharp .avif() encoding were updated. AVIF defaults: quality from
the user slider, effort 4 (balanced encode speed).

Also fixes pre-existing Biome formatting violations in 5 files
that were blocking a clean lint pass.

apps/web/src/components/tools/split-settings.tsx

@@ -28,9 +28,10 @@ const OUTPUT_FORMATS = [
   { value: "png", label: "PNG" },
   { value: "jpg", label: "JPG" },
   { value: "webp", label: "WebP" },
+  { value: "avif", label: "AVIF" },
 ] as const;
 
-const LOSSY_FORMATS = new Set(["jpg", "webp"]);
+const LOSSY_FORMATS = new Set(["jpg", "webp", "avif"]);
 
 export function SplitSettings() {
   const { files, processing: fileStoreProcessing } = useFileStore();