Fix Credo Design (AliasUsage): add aliases in lib

Add module aliases at top and use short names instead of
fully qualified nested modules across lib/.

lib/mv/application.ex

@@ -5,22 +5,28 @@ defmodule Mv.Application do
 
   use Application
 
+  alias Mv.Helpers.SystemActor
+  alias Mv.Repo
+  alias Mv.Vereinfacht.SyncFlash
+  alias MvWeb.Endpoint
+  alias MvWeb.Telemetry
+
   @impl true
   def start(_type, _args) do
-    Mv.Vereinfacht.SyncFlash.create_table!()
+    SyncFlash.create_table!()
 
     children = [
-      MvWeb.Telemetry,
-      Mv.Repo,
+      Telemetry,
+      Repo,
       {Task.Supervisor, name: Mv.TaskSupervisor},
       {DNSCluster, query: Application.get_env(:mv, :dns_cluster_query) || :ignore},
       {Phoenix.PubSub, name: Mv.PubSub},
       {AshAuthentication.Supervisor, otp_app: :my},
-      Mv.Helpers.SystemActor,
+      SystemActor,
       # Start a worker by calling: Mv.Worker.start_link(arg)
       # {Mv.Worker, arg},
       # Start to serve requests, typically the last entry
-      MvWeb.Endpoint
+      Endpoint
     ]
 
     # See https://hexdocs.pm/elixir/Supervisor.html