Add sensor variance config and smooth heat-rate estimate

[Sensor] - replace TempSensorSim's hardcoded k_noise with configurable
temp_offset/variance, accept **kwargs on Max31865 too so both sensors
share a constructor signature usable from TempSensorFactory.create()
[Temp Controller] - low-pass filter the backward-difference heat-rate
estimate (alpha=0.1) in both temp_controller.py and
temp_controller_smith.py instead of using the raw, noisy derivative
[Pot] - drop kn from demo_pot.py's params, matching the unused-field
removal already made to pot.py itself

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

components/sensor/tempSensorSim.py

@@ -6,13 +6,14 @@ class TempSensorSim(ATemperatureSensor):
 	def name(self):
 		return "FakeTemp"
 
-	def __init__(self, *args, **kwargs):
+	def __init__(self, temp_offset=0.0, variance=0.0, **kwargs):
 		ATemperatureSensor.__init__(self)
 		self.temp_set = 19.99
-		self.k_noise = 0.01
+		self.offset = temp_offset
+		self.variance = variance
 
 	def set_fake_temp(self, temp):
 		self.temp_set = temp
 
 	def temperature(self):
-		return self.temp_set + self.k_noise * np.random.normal(0, 1) / np.sqrt(12.0)
+		return self.temp_set + self.offset+ self.variance * np.random.normal(0, 1) / np.sqrt(12.0)