Allow dots in app names (closes #260)

App names may now contain dots, such as sneak.berlin: runs of
lowercase letters and numbers joined by single dots or by hyphens,
2 to 63 characters. Docker accepts every such name in the app's image
name, upaas-<name>; a dot needs a letter or number on both sides
because Docker requires it. The rule also keeps a dot off either end,
so the name is safe as a directory and log file name.

The new and edit app forms use the same pattern. Their old one was not
a valid regular expression under the flag browsers compile it with, so
browsers ignored it.

A test creates an app named sneak.berlin through the new app form,
then builds and deploys it against the fake Docker API and checks the
image and container names with Docker's own rules.

Model: opus-5-5

internal/service/deploy/deploy_app_name_test.go

@@ -101,6 +101,7 @@ func createAppWithForm(
 		t.Context(), http.MethodPost, "/apps", strings.NewReader(form.Encode()),
 	)
 	request.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+
 	recorder := httptest.NewRecorder()
 
 	handlersInstance.HandleAppCreate().ServeHTTP(recorder, request)