feat: add Playwright E2E and API regression test suite

Production-ready test infrastructure with Page Object Model pattern,
reusable fixtures for auth/DB/test-data, and example tests covering
login flow, dashboard, accounts CRUD API, and visual regression.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/e2e/visual.spec.ts

@@ -0,0 +1,53 @@
+/**
+ * Visual regression tests using Playwright's toHaveScreenshot().
+ *
+ * These capture pixel-level snapshots and compare against baselines.
+ * First run creates the baseline images in tests/e2e/visual.spec.ts-snapshots/.
+ *
+ * Update baselines: npx playwright test tests/e2e/visual.spec.ts --update-snapshots
+ */
+
+import { test, expect } from '@playwright/test';
+import { LoginPage } from '../page-objects';
+
+// Use a clean context for login page screenshots
+test.use({ storageState: { cookies: [], origins: [] } });
+
+test.describe('Visual Regression', () => {
+  test('login page should match baseline', async ({ page }) => {
+    const loginPage = new LoginPage(page);
+    await loginPage.goto();
+    await loginPage.waitForReady();
+
+    // Wait for any animations to settle
+    await page.waitForTimeout(500);
+
+    await expect(page).toHaveScreenshot('login-page.png', {
+      fullPage: true,
+      // Mask dynamic content that changes between runs
+      mask: [
+        // Mask any CSRF tokens or dynamic ids in the DOM
+        page.locator('input[type="hidden"]'),
+      ],
+    });
+  });
+});
+
+test.describe('Authenticated Visual Regression', () => {
+  test('dashboard should match baseline', async ({ page }) => {
+    await page.goto('/dashboard');
+    await page.waitForLoadState('networkidle');
+
+    // Wait for charts/data to render
+    await page.waitForTimeout(1_000);
+
+    await expect(page).toHaveScreenshot('dashboard.png', {
+      fullPage: true,
+      // Mask dates and dynamic numbers that change between runs
+      mask: [
+        page.locator('time'),
+        page.locator('[data-testid="current-date"]'),
+      ],
+    });
+  });
+});