Convert Projects module to MediatR commands/queries

Replaces IProjectService/ProjectService. IProjectMemberService is
left in place for now — ProjectMembersController still depends on it
until the next task converts it too.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

mws.application/Projects/ProjectAccess.cs

@@ -0,0 +1,13 @@
+using Mws.Application.Common;
+using Mws.Domain.Projects;
+
+namespace Mws.Application.Projects;
+
+internal static class ProjectAccess
+{
+    public static async Task<Project> GetForUserOrThrowAsync(IUnitOfWork uow, Guid userId, Guid projectId, CancellationToken ct)
+    {
+        return await uow.Projects.GetForUserAsync(userId, projectId, ct)
+            ?? throw new NotFoundException("Project not found");
+    }
+}