Build the heater/pot/sensor rig as one unit, picked by plant_name alone

heater_name/sensor_name/plant_name were three independent config keys,
each picked via its own factory - in practice sim and real hardware
are never actually mixed and matched, so this could (nonsensically)
disagree, e.g. a real heater paired with a simulated sensor.

Add PlantFactory (components/plant/plant_factory.py): plant_name alone
now builds the whole rig together. "sim" gets HeaterSim/Pot (the
modeled plant, as before)/TempSensorSim. Anything else gets
HeaterHendi/PotReal/TempSensor_max31865 - PotReal is a new, deliberately
unmodeled Pot for the real, physical kettle (components/plant/pot_real.py):
the real temperature comes straight from the real sensor, not from a
model, so it just accepts and ignores set_plant_params()/
set_ambient_temperature()/initial() and reports no temperature of its
own, satisfying PotTask/SudTask's interface with nothing to actually
simulate.

heater_name/sensor_name are gone from config.json.templ; server/brewpi.py
delegates to HeaterFactory/TempSensorFactory lazily from inside
PlantFactory, same as before, so real hardware's spidev/pyserial deps
still aren't needed just to import the module.

components/plant/__init__.py

@@ -1 +1,3 @@
 from components.plant.pot import *
+from components.plant.pot_real import *
+from components.plant.plant_factory import *

components/plant/plant_factory.py

@@ -0,0 +1,30 @@
+from components.actor import HeaterFactory
+from components.sensor import TempSensorFactory
+from components.plant.pot import Pot
+from components.plant.pot_real import PotReal
+
+
+class PlantFactory:
+	"""Builds the heater/pot/sensor trio together, as one consistent rig,
+	rather than each picked independently via its own *_name config key -
+	sim and real hardware are never actually mixed and matched in
+	practice, so Controller.plant_name alone now decides all three (see
+	server/brewpi.py).
+
+	Delegates the actual construction to HeaterFactory/TempSensorFactory
+	rather than importing HeaterHendi/TempSensor_max31865 directly, so
+	those classes' hardware-only deps (spidev, pyserial) stay lazily
+	imported - only actually needed when plant_name picks the real rig."""
+
+	@staticmethod
+	def create(plant_name, dt, heater_config):
+		if "sim" in plant_name:
+			heater = HeaterFactory.create("sim", heater_config)
+			pot = Pot(dt)
+			sensor = TempSensorFactory.create("sim", temp_offset=-0.15, variance=0.01)
+			return heater, pot, sensor
+
+		heater = HeaterFactory.create("Hendi", heater_config)
+		pot = PotReal()
+		sensor = TempSensorFactory.create("max31865", temp_offset=-0.15)
+		return heater, pot, sensor

components/plant/pot_real.py

@@ -0,0 +1,46 @@
+from components.aplant import APlant
+
+
+class PotReal(APlant):
+	"""The real kettle - unlike Pot (components/plant/pot.py), this doesn't
+	model the plant's thermal behavior at all: the real kettle does its
+	own physics, and the real temperature comes straight from the real
+	temperature sensor, not from here (see PlantFactory). Exists purely so
+	a real rig still satisfies the same informal interface PotTask/
+	SudTask expect from a Pot - set_plant_params()/set_ambient_temperature()/
+	initial() are accepted and ignored, and get_temperature() has nothing
+	to report."""
+
+	def __init__(self):
+		APlant.__init__(self)
+		self.p_in = 0
+
+	def is_configured(self):
+		return True
+
+	def set_plant_params(self, params):
+		pass
+
+	def set_ambient_temperature(self, theta_amb):
+		pass
+
+	def initial(self, temp):
+		pass
+
+	def activate(self, enable):
+		pass
+
+	def is_activated(self):
+		return True
+
+	def process(self):
+		pass
+
+	def set_power(self, power):
+		self.p_in = power
+
+	def get_power(self):
+		return round(self.p_in, 1)
+
+	def get_temperature(self):
+		return None