feat(web): Playwright E2E test suite for critical paths (#152)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/web/playwright.config.ts

@@ -0,0 +1,32 @@
+import { defineConfig, devices } from '@playwright/test';
+
+/**
+ * Playwright E2E configuration for Mosaic web app.
+ *
+ * Assumes:
+ *   - Next.js web app running on http://localhost:3000
+ *   - NestJS gateway running on http://localhost:4000
+ *
+ * Run with:   pnpm --filter @mosaic/web test:e2e
+ */
+export default defineConfig({
+  testDir: './e2e',
+  fullyParallel: true,
+  forbidOnly: !!process.env['CI'],
+  retries: process.env['CI'] ? 2 : 0,
+  workers: process.env['CI'] ? 1 : undefined,
+  reporter: 'html',
+  use: {
+    baseURL: process.env['PLAYWRIGHT_BASE_URL'] ?? 'http://localhost:3000',
+    trace: 'on-first-retry',
+    screenshot: 'only-on-failure',
+  },
+  projects: [
+    {
+      name: 'chromium',
+      use: { ...devices['Desktop Chrome'] },
+    },
+  ],
+  // Do NOT auto-start the dev server — tests assume it is already running.
+  // webServer is intentionally omitted so tests can run against a live env.
+});