Add integration + Playwright smoke suite for post-deploy QA validation

Existing coverage was one integration test and zero e2e tests. Adds the thin,
high-value integration/e2e layer unit tests can't reach (real Postgres wire
contract, real browser flows) and wires it as a post-deploy smoke gate.

- Seed a deterministic dev/QA admin user and fixed Development env key so
  HTTP-only tests can authenticate without per-run registration.
- Expand the API integration suite: disabled-flag, unauthorized access,
  environment-document bootstrap, identity-override precedence, and auth
  login scenarios, reusing the existing black-box HTTP+Npgsql harness.
- Add a Playwright suite for the admin SPA: login, nav, project/environment
  context selection, and feature create/toggle, against the real API.
- Bind QA Postgres to 127.0.0.1 for direct seeding, add smoke-qa.sh and an
  ensure_node() bootstrap (the qa runner has no Node today), and wire a new
  smoke-qa CI job after deploy-qa.

src/admin/playwright.config.ts

@@ -0,0 +1,29 @@
+import { defineConfig, devices } from '@playwright/test';
+
+/**
+ * Smoke-test suite for the admin SPA. Runs against a real, already-running deployment
+ * (local dev server or a deployed QA environment) — it does not mock the API and does not
+ * start any servers itself. See e2e/global-setup.ts for how authentication is bootstrapped.
+ */
+export default defineConfig({
+  testDir: './e2e',
+  testMatch: '**/*.e2e.ts',
+  fullyParallel: false,
+  forbidOnly: !!process.env.CI,
+  retries: process.env.CI ? 1 : 0,
+  workers: 1,
+  reporter: process.env.CI ? [['list'], ['html', { open: 'never' }]] : 'list',
+  globalSetup: './e2e/global-setup.ts',
+  timeout: 30_000,
+  use: {
+    baseURL: process.env.E2E_BASE_URL ?? 'http://localhost:5173',
+    trace: 'retain-on-failure',
+    screenshot: 'only-on-failure',
+  },
+  projects: [
+    {
+      name: 'chromium',
+      use: { ...devices['Desktop Chrome'] },
+    },
+  ],
+});