fix(ui): polish create flows and terminal navigation

Open the global terminal outside Livewire navigation, clarify that
image tag and SHA256 digest are mutually exclusive, inset the GitLab
empty state, and show loading on Dockerfile create. Add regression tests.

tests/Feature/SimpleDockerfileCreateViewTest.php

@@ -0,0 +1,7 @@
+<?php
+
+it('shows a loading indicator while creating the application', function () {
+    $view = file_get_contents(resource_path('views/livewire/project/new/simple-dockerfile.blade.php'));
+
+    expect($view)->toContain('<x-forms.button type="submit" wire:target="submit" isHighlighted>');
+});