feat: add Storybook with component stories

Installs @storybook/nextjs-vite. Stories co-located with components,
grouped by layer (Shared/Entities/Widgets). Multi-variant cases use
render functions instead of one story per variant/size.

src/entities/project/ui/ProjectCard.stories.tsx

@@ -0,0 +1,37 @@
+import type { Meta, StoryObj } from '@storybook/nextjs-vite'
+import { ProjectCard } from './ProjectCard'
+
+const meta: Meta<typeof ProjectCard> = {
+  title: 'Entities/ProjectCard',
+  component: ProjectCard,
+  decorators: [
+    (Story) => (
+      <div className="p-8 bg-white max-w-md">
+        <Story />
+      </div>
+    ),
+  ],
+}
+
+export default meta
+
+type Story = StoryObj<typeof ProjectCard>
+
+export const Default: Story = {
+  args: {
+    title: 'Portfolio Website',
+    year: '2024',
+    description: 'A brutalist portfolio site built with Next.js and Tailwind CSS.',
+    tags: ['React', 'TypeScript', 'Next.js'],
+  },
+}
+
+export const WithImage: Story = {
+  args: {
+    title: 'Portfolio Website',
+    year: '2024',
+    description: 'A brutalist portfolio site built with Next.js and Tailwind CSS.',
+    tags: ['React', 'TypeScript', 'Next.js'],
+    imageUrl: 'https://placehold.co/800x450/3B4A59/D9B48F?text=Project',
+  },
+}