fix: zero heater power / stirrer rpm on manual disconnect

A manual Disconnect command left the last commanded power/speed in
place server-side, so a reconnect (or the UI's PowerSet/Speed echo)
could show a stale nonzero setpoint for a device that's no longer
attached.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5WEDCc4v473DKqSaQhTQt

tasks/heater.py

@@ -79,6 +79,8 @@ class HeaterTask(ATask):
 			elif pair[0] == 'Disconnect':
 				self.device.activate(False)
 				self.device.disconnect()
+				self.power_soll = 0
+				self.power_set_changed(0)
 			elif 'Power' in pair[0]:
 				self.power_soll = pair[1]
 

tasks/stirrer.py

@@ -45,6 +45,7 @@ class StirrerTask(ATask):
 			elif pair[0] == 'Disconnect':
 				self.device.activate(False)
 				self.device.disconnect()
+				self.device.set_speed(0.0)
 			elif 'Speed' in pair[0]:
 				self.device.set_speed(pair[1])