Add an enable/disable switch for the temperature controller

New TempControllerBase.enabled (default False) forces y=0 in
process_pid() when off, same mechanism as the existing cooling
override - the controller tries not to drive the heater at all.

tasks/tempctrl.py: new 'Enable' recv command and 'Enabled' broadcast
on the TempCtrl channel. tasks/sud.py: SudTask now enables the
controller on any non-IDLE/DONE Sud state and disables it (forcing
power back to 0) on IDLE/DONE, so automatic mode owns it for the
duration of a run and hands back manual control once it stops/finishes.

gui: new "Enabled" checkbox on the Manual tab's Controller group,
synced from the server; the temp/heatrate setpoint controls are
disabled whenever the controller itself is disabled.

client/brewpi_gui.py

@@ -252,6 +252,9 @@ class Window(QtWidgets.QMainWindow, Ui_MainWindow):
 		self.sud_empty = True
 		self.sud_state = None
 		self.sud_user_message = None
+		# Mirrors the server's TempController.enabled - gates the
+		# temp/heatrate setpoint controls (see on_tempctrl_changed()).
+		self.tc_enabled = False
 		# Global, not Sud-specific - from the 'System' channel's one-time
 		# startup message. warp_factor defaults to 1.0 (no scaling) until
 		# that arrives, or for a server that doesn't send it at all.
@@ -295,6 +298,9 @@ class Window(QtWidgets.QMainWindow, Ui_MainWindow):
 		self.msg_system.set_recv_handler(self.on_system_changed)
 
 		self.setupUi(self)
+		# Matches tc_enabled's default (False) until the server says otherwise.
+		self.Slider_temp_soll.setEnabled(False)
+		self.doubleSpinBox_heatrate_soll.setEnabled(False)
 		# Permanent (right-aligned, not cleared by showMessage()/clearMessage())
 		# label for static environment info - distinct from the status bar's
 		# transient step/schedule messages.
@@ -329,6 +335,7 @@ class Window(QtWidgets.QMainWindow, Ui_MainWindow):
 
 		self.checkbox_heater_activate.stateChanged.connect(self.on_checkbox_changed)
 		self.checkbox_stirrer_activate.stateChanged.connect(self.on_checkbox_stirrer_activate_changed)
+		self.checkbox_tc_enable.stateChanged.connect(self.on_checkbox_tc_enable_changed)
 		self.lineEdit_ambient.returnPressed.connect(self.on_ambient_entry_changed)
 		self.btn_pot_reset.clicked.connect(self.on_action_pot_reset)
 		# Only meaningful (and only shown) once the server confirms its Pot
@@ -469,6 +476,12 @@ class Window(QtWidgets.QMainWindow, Ui_MainWindow):
 			self.sud_empty = True
 			self.sud_state = None
 			self.sud_user_message = None
+			self.tc_enabled = False
+			self.checkbox_tc_enable.blockSignals(True)
+			self.checkbox_tc_enable.setChecked(False)
+			self.checkbox_tc_enable.blockSignals(False)
+			self.Slider_temp_soll.setEnabled(False)
+			self.doubleSpinBox_heatrate_soll.setEnabled(False)
 			self.ambient_temp = None
 			self.lineEdit_ambient.clear()
 			self.btn_pot_reset.setVisible(False)
@@ -577,6 +590,10 @@ class Window(QtWidgets.QMainWindow, Ui_MainWindow):
 		print("on_checkbox_stirrer_activate_changed {}".format(value))
 		self.msg_stirrer.send({'Activate': int(value == 2)})
 
+	def on_checkbox_tc_enable_changed(self, value):
+		print("on_checkbox_tc_enable_changed {}".format(value))
+		self.msg_tempctrl.send({'Enable': value == 2})
+
 	def on_action_sud_start(self):
 		self.msg_sud.send({'Start': True})
 
@@ -661,6 +678,13 @@ class Window(QtWidgets.QMainWindow, Ui_MainWindow):
 								self.doubleSpinBox_heatrate_soll.blockSignals(True)
 								self.doubleSpinBox_heatrate_soll.setValue(subsubmsg['Set'])
 								self.doubleSpinBox_heatrate_soll.blockSignals(False)
+			elif "Enabled" in key:
+				self.tc_enabled = msg['Enabled']
+				self.checkbox_tc_enable.blockSignals(True)
+				self.checkbox_tc_enable.setChecked(self.tc_enabled)
+				self.checkbox_tc_enable.blockSignals(False)
+				self.Slider_temp_soll.setEnabled(self.tc_enabled)
+				self.doubleSpinBox_heatrate_soll.setEnabled(self.tc_enabled)
 			if "Ist" in key:
 				submsg = msg['Ist']
 				if 'Temp' in submsg: