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/homepage.spec.ts

@@ -0,0 +1,38 @@
+import { test, expect } from '@playwright/test';
+
+test.describe('Homepage', () => {
+  test('loads and renders the hero section', async ({ page }) => {
+    await page.goto('/');
+    // Wait for the hero section to appear
+    const hero = page.locator('.hero');
+    await expect(hero).toBeVisible();
+  });
+
+  test('shows the site title in the hero', async ({ page }) => {
+    await page.goto('/');
+    const title = page.locator('.hero__title');
+    await expect(title).toBeVisible();
+    const text = await title.textContent();
+    expect(text).toBeTruthy();
+  });
+
+  test('has navigation links in the header', async ({ page }) => {
+    await page.goto('/');
+    const nav = page.locator('.header__nav');
+    await expect(nav).toBeVisible();
+
+    // Should have at least the Home and About links
+    const links = nav.locator('.header__nav-link');
+    const count = await links.count();
+    expect(count).toBeGreaterThanOrEqual(2);
+  });
+
+  test('hero nav links are present for subpages', async ({ page }) => {
+    await page.goto('/');
+    const heroNav = page.locator('.hero__nav');
+    await expect(heroNav).toBeVisible();
+    const links = heroNav.locator('.hero__nav-link');
+    const count = await links.count();
+    expect(count).toBeGreaterThanOrEqual(1);
+  });
+});