refactor: replace plant_name with per-component type keys in config

PlantFactory.create() no longer takes plant_name; sim vs real is derived
from Heater.type. StirrerFactory is wired from Stirrer.type. HeaterFactory
registry key lowercased to "hendi" to match config. Controller.plant_name
removed from both config templates.

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

config-real.json.tpl

@@ -1,7 +1,6 @@
 {
 	"ambient_temperature": 20,
 	"Controller" : {
-	"plant_name": "real",
 	"pid_type": "Smith"
 	},
  	"TempCtrl": {