Give the empty projects state a create-project action

[T0nyzz]

Problem

On a relay with no projects yet, there is no way to create your first project.

ProjectsView returns EmptyState from an early return at ProjectsView.tsx:594:

if (projects.length === 0) {
  return <EmptyState />;
}

That happens before the create menu and CreateProjectDialog are mounted (further down, around line 790), and EmptyState itself renders only an icon and the text "No projects yet · Projects published to this relay will appear here." — no action.

So the create control only appears once you already have a project.

There is no other entry point: CreateProjectDialog is mounted solely in ProjectsView, and AddProjectRepositoryDialog / AttachProjectRepositoryDialog live in ProjectRepositoryManagement, which is inside a project detail screen you cannot reach without an existing project.

Reproduce: open Projects on a relay with zero projects. There is no create affordance anywhere.

Fix

EmptyState now takes a required onCreateProject callback and renders a Create project button. ProjectsView wires it to the same handler and dialog the pinned create menu uses, and mounts CreateProjectDialog in the empty-state branch so the button opens something.

The prop is required rather than optional deliberately. EmptyState has exactly one call site, so making it required turns dropped wiring at that call site into a compile error instead of a silent regression — which is precisely the failure this PR is fixing.

Testing

• ProjectCards.test.mjs — new coverage asserting the empty state renders a create action and invokes the callback
• tsc --noEmit clean
• biome check clean on all three changed files
• Full suite: 4792 passing, 0 failing