feat: add Skeleton loading-placeholder primitive

A reusable, token-driven shimmer block with configurable width/height,
radius, and variant. Decorative (aria-hidden) — loading state is announced
by the container. Freezes to a solid muted block under the global
prefers-reduced-motion override.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/Cargo.lock

@@ -1558,7 +1558,7 @@ checksum = "c41e0c4fef86961ac6d6f8a82609f55f31b05e4fce149ac5710e439df7619ba4"
 
 [[package]]
 name = "mangalord"
-version = "0.109.1"
+version = "0.110.0"
 dependencies = [
  "anyhow",
  "argon2",

backend/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "mangalord"
-version = "0.109.1"
+version = "0.110.0"
 edition = "2021"
 default-run = "mangalord"
 

frontend/package.json

@@ -1,6 +1,6 @@
 {
   "name": "mangalord-frontend",
-  "version": "0.109.1",
+  "version": "0.110.0",
   "private": true,
   "type": "module",
   "scripts": {

frontend/src/lib/components/Skeleton.svelte

@@ -0,0 +1,85 @@
+<script lang="ts">
+    /**
+     * Decorative loading placeholder. Renders a muted block with a subtle
+     * shimmer that sweeps across it. Purely visual — `aria-hidden` keeps it
+     * out of the accessibility tree; the loading state should be announced by
+     * the container (e.g. `role="status"`).
+     *
+     * The shimmer freezes to a solid `--surface-elevated` block under the
+     * global `prefers-reduced-motion` override (see tokens.css), which is the
+     * intended reduced-motion appearance.
+     */
+    let {
+        width = '100%',
+        height,
+        radius = 'md',
+        variant = 'block',
+        testid
+    }: {
+        width?: string;
+        height?: string;
+        /** Corner radius, mapped to the design-token scale. */
+        radius?: 'sm' | 'md' | 'lg' | 'pill';
+        /** `circle` forces a pill radius (for avatars / dots). */
+        variant?: 'block' | 'text' | 'circle';
+        testid?: string;
+    } = $props();
+
+    const radiusClass = $derived(variant === 'circle' ? 'radius-pill' : `radius-${radius}`);
+
+    const style = $derived(
+        [`width: ${width};`, height ? `height: ${height};` : null].filter(Boolean).join(' ')
+    );
+</script>
+
+<span
+    class="skeleton {radiusClass}"
+    class:text={variant === 'text'}
+    data-testid={testid}
+    aria-hidden="true"
+    {style}
+></span>
+
+<style>
+    .skeleton {
+        display: block;
+        /* Static base so the reduced-motion freeze reads as a clean block
+           rather than a stalled mid-keyframe gradient. */
+        background-color: var(--surface-elevated);
+        background-image: linear-gradient(
+            90deg,
+            var(--surface) 0%,
+            var(--surface-elevated) 50%,
+            var(--surface) 100%
+        );
+        background-size: 200% 100%;
+        background-repeat: no-repeat;
+        animation: skeleton-shimmer 1.2s ease-in-out infinite;
+    }
+
+    .skeleton.text {
+        height: 0.9em;
+    }
+
+    .radius-sm {
+        border-radius: var(--radius-sm);
+    }
+    .radius-md {
+        border-radius: var(--radius-md);
+    }
+    .radius-lg {
+        border-radius: var(--radius-lg);
+    }
+    .radius-pill {
+        border-radius: var(--radius-pill);
+    }
+
+    @keyframes skeleton-shimmer {
+        from {
+            background-position: 200% 0;
+        }
+        to {
+            background-position: -200% 0;
+        }
+    }
+</style>

frontend/src/lib/components/Skeleton.svelte.test.ts

@@ -0,0 +1,49 @@
+import { describe, it, expect, afterEach } from 'vitest';
+import { render, screen, cleanup } from '@testing-library/svelte';
+import Skeleton from './Skeleton.svelte';
+
+afterEach(() => cleanup());
+
+describe('Skeleton primitive', () => {
+    it('renders an element carrying the given testid', () => {
+        render(Skeleton, { props: { testid: 'sk' } });
+        expect(screen.getByTestId('sk')).toBeTruthy();
+    });
+
+    it('is decorative (aria-hidden) so screen readers ignore it', () => {
+        render(Skeleton, { props: { testid: 'sk' } });
+        expect(screen.getByTestId('sk').getAttribute('aria-hidden')).toBe('true');
+    });
+
+    it('applies width and height as inline styles', () => {
+        render(Skeleton, { props: { testid: 'sk', width: '120px', height: '2rem' } });
+        const el = screen.getByTestId('sk') as HTMLElement;
+        expect(el.style.width).toBe('120px');
+        expect(el.style.height).toBe('2rem');
+    });
+
+    it('defaults width to 100% when omitted', () => {
+        render(Skeleton, { props: { testid: 'sk' } });
+        expect((screen.getByTestId('sk') as HTMLElement).style.width).toBe('100%');
+    });
+
+    it('maps the radius prop to a radius class', () => {
+        render(Skeleton, { props: { testid: 'sk', radius: 'lg' } });
+        expect(screen.getByTestId('sk').classList.contains('radius-lg')).toBe(true);
+    });
+
+    it('defaults to the md radius', () => {
+        render(Skeleton, { props: { testid: 'sk' } });
+        expect(screen.getByTestId('sk').classList.contains('radius-md')).toBe(true);
+    });
+
+    it('renders a pill radius for the circle variant', () => {
+        render(Skeleton, { props: { testid: 'sk', variant: 'circle' } });
+        expect(screen.getByTestId('sk').classList.contains('radius-pill')).toBe(true);
+    });
+
+    it('carries the skeleton base class for the shimmer', () => {
+        render(Skeleton, { props: { testid: 'sk' } });
+        expect(screen.getByTestId('sk').classList.contains('skeleton')).toBe(true);
+    });
+});