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%.
