server: graceful Ctrl-C shutdown; HendiCtrl closes connection cleanly

On KeyboardInterrupt, brewpi.py cancels all asyncio tasks (letting
HeaterTask's `with device.open()` finally block run), then calls
heater.close() as belt-and-suspenders before closing the event loop.

On shutdown HeaterHendi.activate(False) now sets the switch to 0 instead
of disabling remote control, so the Hendi stays in remote mode at 0 W
rather than dropping back to its local panel state.  HendiCtrl.close()
does the same (setSwitch(0)) then closes the serial port.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

components/actor/heater_hendi.py

@@ -24,7 +24,7 @@ class HeaterHendi(AHeater):
 		if enable:
 			self.hendi.remoteEnable(1)
 		else:
-			self.hendi.remoteEnable(0)
+			self.hendi.setSwitch(0)
 
 	def is_activated(self):
 		s = self.hendi.isRemoteEnable()
@@ -44,3 +44,6 @@ class HeaterHendi(AHeater):
 
 	def get_power(self):
 		return self.power_eff
+
+	def close(self):
+		self.hendi.close()

components/actor/hendiCtrl.py

@@ -183,6 +183,13 @@ class HendiCtrl:
 	def getPowerWatts(self):
 		return int(self.toWatts(self.getPowerDigits()) + 0.5)
 
+	def close(self):
+		try:
+			self.setSwitch(0)
+		except Exception:
+			pass
+		self.ser.close()
+
 
 if __name__ == '__main__':