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.

tests/api/MicCheck.Api.Tests.Integration/Auth/AuthTests.cs

@@ -0,0 +1,95 @@
+using System.Text.Json;
+using MicCheck.Api.Tests.Integration.Common;
+using NUnit.Framework;
+
+namespace MicCheck.Api.Tests.Integration.Auth;
+
+[TestFixture]
+public class AuthTests
+{
+    private const string Password = "Integration!Test123";
+
+    private IntegrationTestSettings settings = null!;
+    private TestDatabase db = null!;
+    private FlagApiHttpClient client = null!;
+    private AuthSeed? seed;
+
+    [OneTimeSetUp]
+    public void OneTimeSetUp()
+    {
+        settings = IntegrationTestSettings.Load();
+        db = new TestDatabase(settings.DbConnectionString);
+        client = new FlagApiHttpClient(settings);
+    }
+
+    [OneTimeTearDown]
+    public void OneTimeTearDown() => client.Dispose();
+
+    [SetUp]
+    public async Task SetUp()
+        => seed = await AuthSeed.InsertAsync(db, testRunTag: "Auth", password: Password);
+
+    [TearDown]
+    public async Task TearDown()
+    {
+        if (seed is not null)
+        {
+            await seed.CleanupAsync(db);
+            seed = null;
+        }
+    }
+
+    [Test]
+    public async Task WhenValidCredentialsAreSubmitted_ThenLoginReturnsAnAccessToken()
+    {
+        var current = seed!;
+
+        using var response = await client.SendAsync(
+            httpFile: "Auth.http",
+            requestName: "Login",
+            variables: new Dictionary<string, string>
+            {
+                ["baseUrl"] = settings.BaseUrl,
+                ["email"] = current.Email,
+                ["password"] = current.Password
+            });
+
+        var body = await response.Content.ReadAsStringAsync();
+
+        Assert.That(
+            response.IsSuccessStatusCode,
+            Is.True,
+            $"POST /api/v1/auth/login returned {(int)response.StatusCode} {response.ReasonPhrase} for a valid seeded user. Body: {body}");
+
+        var login = JsonSerializer.Deserialize<LoginResponseDto>(body, JsonOptions)
+            ?? throw new InvalidOperationException("Response body was not the expected login shape.");
+
+        Assert.That(login.AccessToken, Is.Not.Null.And.Not.Empty);
+        Assert.That(login.RefreshToken, Is.Not.Null.And.Not.Empty);
+    }
+
+    [Test]
+    public async Task WhenAnIncorrectPasswordIsSubmitted_ThenLoginIsUnauthorized()
+    {
+        var current = seed!;
+
+        using var response = await client.SendAsync(
+            httpFile: "Auth.http",
+            requestName: "Login",
+            variables: new Dictionary<string, string>
+            {
+                ["baseUrl"] = settings.BaseUrl,
+                ["email"] = current.Email,
+                ["password"] = "definitely-the-wrong-password"
+            });
+
+        Assert.That(
+            (int)response.StatusCode,
+            Is.EqualTo(401),
+            $"Expected 401 for an incorrect password, got {(int)response.StatusCode} {response.ReasonPhrase}.");
+    }
+
+    private static readonly JsonSerializerOptions JsonOptions = new(JsonSerializerDefaults.Web);
+
+    private sealed record LoginResponseDto(string AccessToken, string RefreshToken, DateTime ExpiresAt);
+}