feat(agent): expose compile-time version

agent/lib/proxmox_agent.ex

@@ -1,18 +1,8 @@
 defmodule ProxmoxAgent do
-  @moduledoc """
-  Documentation for `ProxmoxAgent`.
-  """
+  @moduledoc "Top-level namespace. Exposes the compiled version for reporting."
 
-  @doc """
-  Hello world.
+  @version Mix.Project.config()[:version]
 
-  ## Examples
-
-      iex> ProxmoxAgent.hello()
-      :world
-
-  """
-  def hello do
-    :world
-  end
+  @spec version() :: String.t()
+  def version, do: @version
 end