fix: remove duplicate handle_info and schedule_cleanup function definitions in AgentCache (#162)

Removed duplicate function definitions that were causing compile warnings:
- handle_info(:cleanup_expired, state) was defined twice (lines 94 and 110)
- schedule_cleanup/0 was defined twice (lines 105 and 121)

The duplicate definitions at lines 110-124 were exact copies and have been removed.

Reviewed-on: graham/towerops-web#162

lib/towerops/agents/agent_cache.ex

@@ -105,21 +105,4 @@ defmodule Towerops.Agents.AgentCache do
   defp schedule_cleanup do
     Process.send_after(self(), :cleanup_expired, 60_000)
   end
-
-  @impl GenServer
-  def handle_info(:cleanup_expired, state) do
-    now = System.monotonic_time(:millisecond)
-    # Delete all device cache entries that have expired
-    :ets.select_delete(@table, [
-      {{{:device, :_}, :_, :"$1"}, [{:<, :"$1", now}], [true]}
-    ])
-
-    schedule_cleanup()
-    {:noreply, state}
-  end
-
-  defp schedule_cleanup do
-    # Run cleanup every minute
-    Process.send_after(self(), :cleanup_expired, 60_000)
-  end
 end