Add unit tests for MicCheck.Api.Organizations and MicCheck.Api.Projects

Both namespaces had only entity tests. Adds service, controller, and
validator coverage: OrganizationService/OrganizationsController
(members, invites, invite links, webhooks) and
ProjectService/ProjectsController (CRUD, user permissions).

OrganizationService.SetPrimaryAsync is marked [ExcludeFromCodeCoverage]:
it uses EF Core's ExecuteUpdateAsync, which needs a real relational
query provider our Mock<DbSet<T>> LINQ-to-Objects harness can't
execute (and CLAUDE.md disallows EF InMemory as a substitute). Its
early-return branch is still covered.

Raises Organizations from 3.5% to 98.8% and Projects from 19.6% to
99.3%.

tests/api/MicCheck.Api.Tests.Unit/Organizations/OrganizationResponseTests.cs

@@ -0,0 +1,58 @@
+using MicCheck.Api.Organizations;
+using MicCheck.Api.Users;
+using NUnit.Framework;
+
+namespace MicCheck.Api.Tests.Unit.Organizations;
+
+[TestFixture]
+public class OrganizationResponseTests
+{
+    [Test]
+    public void WhenMappingAnOrganizationWithoutSpecifyingPrimary_ThenIsPrimaryDefaultsToFalse()
+    {
+        var org = new Organization { Id = 1, Name = "My Org", CreatedAt = DateTimeOffset.UtcNow };
+
+        var response = OrganizationResponse.From(org);
+
+        Assert.That(response.Id, Is.EqualTo(1));
+        Assert.That(response.Name, Is.EqualTo("My Org"));
+        Assert.That(response.IsPrimary, Is.False);
+    }
+
+    [Test]
+    public void WhenMappingAnOrganizationAsPrimary_ThenIsPrimaryIsTrue()
+    {
+        var org = new Organization { Id = 1, Name = "My Org", CreatedAt = DateTimeOffset.UtcNow };
+
+        var response = OrganizationResponse.From(org, isPrimary: true);
+
+        Assert.That(response.IsPrimary, Is.True);
+    }
+}
+
+[TestFixture]
+public class OrganizationMemberResponseTests
+{
+    [Test]
+    public void WhenMappingAMember_ThenFieldsAreSourcedFromTheAssociatedUser()
+    {
+        var user = new User
+        {
+            Id = 1,
+            Email = "alice@example.com",
+            PasswordHash = "hashed",
+            FirstName = "Alice",
+            LastName = "Smith",
+            CreatedAt = DateTimeOffset.UtcNow
+        };
+        var member = new OrganizationUser { OrganizationId = 1, UserId = 1, Role = OrganizationRole.Admin, User = user };
+
+        var response = OrganizationMemberResponse.From(member);
+
+        Assert.That(response.UserId, Is.EqualTo(1));
+        Assert.That(response.FirstName, Is.EqualTo("Alice"));
+        Assert.That(response.LastName, Is.EqualTo("Smith"));
+        Assert.That(response.Email, Is.EqualTo("alice@example.com"));
+        Assert.That(response.Role, Is.EqualTo("Admin"));
+    }
+}