refactor: drop firmware-version display, move Enable toggle to Controller

Firmware version is already printed to the log at connect() time
(HendiCtrl/Pololu1376) - remove the live GUI/websocket firmware
reporting entirely (Connectable, HeaterHendi/StirrerPololu1376,
Heater/StirrerTask, web GUI) as redundant.

Also move the Heater panel's Closed-loop checkbox into the Controller
panel and rename it "Enable" - the Controller panel now shows a
live Enabled (green) / Disabled (gray) status badge next to its
heading, matching the Connected/Disconnected badges on the Heater/
Stirrer panels.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YaPLuRPpyjWcwhMvCvpHCL

components/actor/heater_hendi.py

@@ -23,13 +23,11 @@ class HeaterHendi(AHeater):
 	def connect(self):
 		ok = self.hendi.connect()
 		self.connected = ok
-		self.firmware_version = self.hendi.sw_ver if ok else None
 		return ok
 
 	def disconnect(self):
 		self.hendi.disconnect()
 		self.connected = False
-		self.firmware_version = None
 
 	def activate(self, enable):
 		if not self.connected:

components/actor/stirrerpololu1376.py

@@ -23,13 +23,11 @@ class StirrerPololu1376(AStirrer):
 	def connect(self):
 		ok = self.drv.connect()
 		self.connected = ok
-		self.firmware_version = self.drv.firmware_version if ok else None
 		return ok
 
 	def disconnect(self):
 		self.drv.disconnect()
 		self.connected = False
-		self.firmware_version = None
 
 	@contextmanager
 	def remote_open(self):