Fix remaining warning and design suggestion

- Fix length/1 check in mobile_channel.ex
- Add LeaderElection alias in connection_manager.ex

All warnings and design suggestions now complete!
Remaining: 40 refactoring opportunities (complex/nested functions)

lib/aprsme/cluster/connection_manager.ex

@@ -5,6 +5,7 @@ defmodule Aprsme.Cluster.ConnectionManager do
   """
   use GenServer
 
+  alias Aprsme.Cluster.LeaderElection
   alias Aprsme.Is.IsSupervisor
 
   require Logger
@@ -26,7 +27,7 @@ defmodule Aprsme.Cluster.ConnectionManager do
 
   @impl true
   def handle_info(:check_initial_state, state) do
-    if Aprsme.Cluster.LeaderElection.leader?() do
+    if LeaderElection.leader?() do
       Logger.info("This node is the leader, starting APRS-IS connection")
       start_aprs_connection()
       {:noreply, %{state | connection_started: true}}

lib/aprsme_web/channels/mobile_channel.ex

@@ -370,7 +370,7 @@ defmodule AprsmeWeb.MobileChannel do
     Logger.info("Loaded #{length(packets)} historical packets for mobile client")
 
     # Send historical packets to client
-    if length(packets) > 0 do
+    if packets != [] do
       # Convert packets to mobile format and send them
       Enum.each(packets, fn packet ->
         packet_data = build_mobile_packet(packet)