스케쥴러 시작/정기 기능 추가

app/controllers/modbus_controller.rb

@@ -1,6 +1,17 @@
 class ModbusController < ApplicationController
   def index
     @schedule = Schedule.all
+    @modbus_running = Modbus::PollingService.running?
+  end
+
+  def start
+    Modbus::PollingService.start
+    redirect_to modbus_index_path
+  end
+
+  def stop
+    Modbus::PollingService.stop
+    redirect_to modbus_index_path
   end
 
   def schedule_edit