feat: visual polish & UX — fade-in, theme toggle, scroll-to-top, footer, cursor, badge

- Add FadeIn component (IntersectionObserver scroll-reveal + load animation)
- Add dark/light theme toggle (useSyncExternalStore + localStorage)
- Add scroll-to-top button (appears after 300px scroll)
- Add configurable footer with social links (gallery.yaml)
- Add crosshair cursor on photo grid items
- Add 'X photos' count badge on subpage cover images
- Add light theme color palette in tokens.css

e2e/about.spec.ts

@@ -0,0 +1,23 @@
+import { test, expect } from '@playwright/test';
+
+test.describe('About page', () => {
+  test('loads and shows the about content', async ({ page }) => {
+    await page.goto('/about');
+    const about = page.locator('.about');
+    await expect(about).toBeVisible();
+  });
+
+  test('has a portrait column', async ({ page }) => {
+    await page.goto('/about');
+    const portrait = page.locator('.about__portrait-col');
+    await expect(portrait).toBeVisible();
+  });
+
+  test('has a text column with name', async ({ page }) => {
+    await page.goto('/about');
+    const name = page.locator('.about__name');
+    await expect(name).toBeVisible();
+    const text = await name.textContent();
+    expect(text).toBeTruthy();
+  });
+});