✨ Add ScrollAreaMask component for customizable scroll masking effects

src/components/ui/scroll-area/scroll-area-mask.svelte

@@ -0,0 +1,50 @@
+<script lang="ts">
+  import { cn } from "@/utils/cn";
+  type Mask = {
+    top: boolean;
+    bottom: boolean;
+    left: boolean;
+    right: boolean;
+  };
+
+  let {
+    showMask,
+    maskHeight,
+    class: className = "",
+  }: {
+    showMask: Mask;
+    maskHeight: number;
+    class?: string;
+  } = $props();
+</script>
+
+<div
+  aria-hidden="true"
+  style={`--top-fade-height: ${showMask.top ? `${maskHeight}px` : "0px"}; --bottom-fade-height: ${showMask.bottom ? `${maskHeight}px` : "0px"};`}
+  class={cn(
+    "pointer-events-none absolute inset-0 z-10",
+    "before:absolute before:inset-x-0 before:top-0 before:transition-[height,opacity] before:duration-300 before:content-['']",
+    "after:absolute after:inset-x-0 after:bottom-0 after:transition-[height,opacity] after:duration-300 after:content-['']",
+    "before:h-(--top-fade-height) after:h-(--bottom-fade-height)",
+    showMask.top ? "before:opacity-100" : "before:opacity-0",
+    showMask.bottom ? "after:opacity-100" : "after:opacity-0",
+    "before:from-background before:bg-gradient-to-b before:to-transparent",
+    "after:from-background after:bg-gradient-to-t after:to-transparent",
+    className,
+  )}
+></div>
+<div
+  aria-hidden="true"
+  style={`--left-fade-width: ${showMask.left ? `${maskHeight}px` : "0px"}; --right-fade-width: ${showMask.right ? `${maskHeight}px` : "0px"};`}
+  class={cn(
+    "pointer-events-none absolute inset-0 z-10",
+    "before:absolute before:inset-y-0 before:left-0 before:transition-[width,opacity] before:duration-300 before:content-['']",
+    "after:absolute after:inset-y-0 after:right-0 after:transition-[width,opacity] after:duration-300 after:content-['']",
+    "before:w-(--left-fade-width) after:w-(--right-fade-width)",
+    showMask.left ? "before:opacity-100" : "before:opacity-0",
+    showMask.right ? "after:opacity-100" : "after:opacity-0",
+    "before:from-background before:bg-gradient-to-r before:to-transparent",
+    "after:from-background after:bg-gradient-to-l after:to-transparent",
+    className,
+  )}
+></div>