Sprint D: hardening e2e, /search redirect, scroll restore fix.

Admin review smoke tests, CWV budgets, unified gallery at /, and explicit
body unlock when closing the photo modal so scroll position restores.

e2e/tests/viewer.web-vitals.spec.ts

@@ -0,0 +1,33 @@
+import { test } from '../fixtures';
+import { BUDGET_MS, expectWithinBudget } from '../timing-budgets';
+import {
+  CWV_BUDGET,
+  expectWithinCwvBudget,
+  installWebVitalsCollector,
+  readWebVitals,
+} from '../web-vitals-budgets';
+
+test.describe('viewer web vitals @smoke', () => {
+  test.beforeEach(async ({ page }) => {
+    await installWebVitalsCollector(page);
+  });
+
+  test('home gallery LCP and CLS within budget', async ({ page, playkitConfig, timings }) => {
+    await timings.measure('open_gallery_cwv', async () => {
+      await page.goto(`${playkitConfig.baseUrl}/`);
+      await page
+        .getByLabel('Account menu')
+        .or(page.getByRole('button', { name: /Sign in/i }))
+        .first()
+        .waitFor({ state: 'visible', timeout: 20_000 });
+    });
+    expectWithinBudget(timings, 'open_gallery_cwv', BUDGET_MS.uiAction);
+
+    const vitals = await readWebVitals(page);
+    expectWithinCwvBudget(vitals);
+    test.info().annotations.push({
+      type: 'cwv',
+      description: `LCP=${Math.round(vitals.lcp)}ms CLS=${vitals.cls.toFixed(3)} budgets LCP<=${CWV_BUDGET.lcp} CLS<=${CWV_BUDGET.cls}`,
+    });
+  });
+});