chore: import upstream snapshot with attribution

apps/sim/blocks/custom/custom-block-icon.tsx

@@ -0,0 +1,55 @@
+'use client'
+
+import { memo, type SVGProps } from 'react'
+import { cn } from '@sim/emcn'
+import { Box } from 'lucide-react'
+import type { BlockIcon } from '@/blocks/types'
+
+/**
+ * Build a `BlockIcon` from an uploaded icon image URL. Rendered as an `<img>` so
+ * any uploaded PNG/JPEG/SVG works; `className` (size) is forwarded like every
+ * other block icon. Cached by URL so the component reference stays stable across
+ * the many tiles/nodes that render a custom block.
+ */
+const cache = new Map<string, BlockIcon>()
+
+export function makeImageIcon(url: string): BlockIcon {
+  const cached = cache.get(url)
+  if (cached) return cached
+
+  // Fill the tile so an uploaded image/logo reads at the same footprint as other
+  // blocks' colored tiles, instead of a small glyph floating in a transparent
+  // square. Trailing `size-full` beats a consumer size *class* (twMerge keeps the
+  // last of a conflict group) so a tiled surface (canvas/toolbar/palette) fills;
+  // it loses to a consumer inline `style` (specificity) so a tile-less inline
+  // surface that sizes via `style={{ width, height }}` still renders at its px.
+  const ImageComponent = memo(({ className, style }: SVGProps<SVGSVGElement>) => (
+    <img
+      src={url}
+      alt=''
+      style={style}
+      className={cn('rounded-[4px] object-contain', className, 'size-full')}
+    />
+  ))
+  // double-cast-allowed: an <img> renderer must satisfy the SVG-typed BlockIcon slot
+  const Icon = ImageComponent as unknown as BlockIcon
+
+  cache.set(url, Icon)
+  return Icon
+}
+
+/** Fallback icon for custom blocks published without an uploaded image. */
+// double-cast-allowed: a lucide icon component fills the SVG-typed BlockIcon slot
+export const DefaultCustomBlockIcon: BlockIcon = Box as unknown as BlockIcon
+
+/**
+ * Resolve a custom block's icon: the uploaded image, else the org's whitelabel logo
+ * (`fallbackUrl`), else the default glyph.
+ */
+export function getCustomBlockIcon(
+  iconUrl: string | null | undefined,
+  fallbackUrl?: string | null
+): BlockIcon {
+  const url = iconUrl || fallbackUrl
+  return url ? makeImageIcon(url) : DefaultCustomBlockIcon
+}