feat(ui): add reusable Skeleton loading component

app/components/Skeleton/Skeleton.module.css

@@ -0,0 +1,63 @@
+.skeleton {
+  display: block;
+  position: relative;
+  overflow: hidden;
+  background-color: var(--skeleton-base, rgba(15, 23, 42, 0.08));
+  border-radius: var(--radius-sm, 6px);
+}
+
+.skeleton::after {
+  content: "";
+  position: absolute;
+  inset: 0;
+  transform: translateX(-100%);
+  background: linear-gradient(
+    90deg,
+    transparent,
+    var(--skeleton-sheen, rgba(255, 255, 255, 0.45)),
+    transparent
+  );
+  animation: skeleton-shimmer 1.4s ease-in-out infinite;
+}
+
+.text { border-radius: var(--radius-sm, 6px); }
+.rect { border-radius: var(--radius-md, 10px); }
+.circle { border-radius: 50%; }
+
+@keyframes skeleton-shimmer {
+  100% { transform: translateX(100%); }
+}
+
+:global([data-theme="dark"]) .skeleton {
+  background-color: var(--skeleton-base-dark, rgba(255, 255, 255, 0.09));
+}
+:global([data-theme="dark"]) .skeleton::after {
+  background: linear-gradient(
+    90deg,
+    transparent,
+    var(--skeleton-sheen-dark, rgba(255, 255, 255, 0.13)),
+    transparent
+  );
+}
+
+@media (prefers-color-scheme: dark) {
+  :global(:root:not([data-theme="light"])) .skeleton {
+    background-color: var(--skeleton-base-dark, rgba(255, 255, 255, 0.09));
+  }
+  :global(:root:not([data-theme="light"])) .skeleton::after {
+    background: linear-gradient(
+      90deg, transparent,
+      var(--skeleton-sheen-dark, rgba(255, 255, 255, 0.13)), transparent
+    );
+  }
+}
+
+@media (prefers-reduced-motion: reduce) {
+  .skeleton::after { animation: none; }
+  .skeleton { animation: skeleton-pulse 1.6s ease-in-out infinite; }
+}
+
+@keyframes skeleton-pulse {
+  0%, 100% { opacity: 1; }
+  50% { opacity: 0.55; }
+}

app/components/Skeleton/Skeleton.tsx

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+import styles from "./Skeleton.module.css";
+
+type SkeletonVariant = "text" | "rect" | "circle";
+
+type SkeletonProps = {
+  /** Width as a CSS value. Numbers are treated as px. Defaults to 100%. */
+  width?: string | number;
+  /** Height as a CSS value. Numbers are treated as px. Defaults to 1rem. */
+  height?: string | number;
+  /** Visual shape of the placeholder. */
+  variant?: SkeletonVariant;
+  /** Optional border-radius override (CSS value / px number). */
+  radius?: string | number;
+  /** Extra class names to merge with the component styles. */
+  className?: string;
+};
+
+const toCssSize = (value?: string | number) =>
+  typeof value === "number" ? `${value}px` : value;
+
+/**
+ * Skeleton — a lightweight, theme-aware loading placeholder.
+ *
+ * Use it while data is loading to reduce layout shift and improve the
+ * perceived performance of data-heavy views (tables, cards, charts).
+ *
+ * @example
+ * <Skeleton width={180} height={20} />
+ * <Skeleton variant="circle" width={40} />
+ * <Skeleton variant="rect" height={120} radius={12} />
+ */
+export function Skeleton({
+  width = "100%",
+  height = "1rem",
+  variant = "text",
+  radius,
+  className,
+}: SkeletonProps) {
+  return (
+    <span
+      className={[styles.skeleton, styles[variant], className]
+        .filter(Boolean)
+        .join(" ")}
+      style={{
+        width: toCssSize(width),
+        // A circle should be a perfect round, so height tracks width.
+        height: variant === "circle" ? toCssSize(width) : toCssSize(height),
+        ...(radius != null ? { borderRadius: toCssSize(radius) } : {}),
+      }}
+      // Purely decorative: keep it out of the accessibility tree.
+      aria-hidden="true"
+    />
+  );
+}
+
+export default Skeleton;