Add Playwright visual smoke test

e2e/home.spec.js

@@ -0,0 +1,13 @@
+// Rôle : vérifie en navigateur que le shell principal se charge pour les diagnostics visuels.
+import { expect, test } from "@playwright/test";
+
+test("home page renders the application shell", async ({ page }) => {
+  await page.goto("/");
+
+  await expect(page.locator(".app-shell")).toBeVisible();
+  await expect(page.locator("main")).toBeVisible();
+  await expect(page).toHaveScreenshot("home.png", {
+    fullPage: true,
+    maxDiffPixelRatio: 0.03
+  });
+});