Refactor sud JSON pot params under a nested 'pot' key

Top-level pot_mass/pot_material/L/Td/grain_mass/water_mass and their
per-step overrides are now grouped under a 'pot' sub-object, matching
the structure already applied to sud_0010.json's parent level. Updated
all sude/*.json files and the parsing/consuming code in components/sud.py,
tasks/sud.py, components/sud_forecast.py, and scripts/demos/sud/demo_sud.py.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T52JH848ojhXXHn1bAzdC3

sude/GuiTest_no_user.json

@@ -1,19 +1,23 @@
 {
 	"Name": "GuiTest - No User",
 	"Description": "Small, fast schedule for exercising the GUI (load/start/pause/stop/restart) without waiting through a real brew",
-	"pot_mass": 5.96,
-	"pot_material": "Edelstahl 18/10",
-	"L": 0.2,
-	"Td": 30,
-	"grain_mass": 5.21,
-	"water_mass": 22,
+	"pot": {
+		"mass": 5.96,
+		"material": "Edelstahl 18/10",
+		"L": 0.2,
+		"Td": 30,
+		"grain_mass": 5.21,
+		"water_mass": 22
+	},
 	"default": {
 		"step": {
 			"descr": "Put description here",
 			"user_message": "Put user message here",
 			"user_wait_for_continue": false,
-			"grain_mass": 5.21,
-			"water_mass": 22,
+			"pot": {
+				"grain_mass": 5.21,
+				"water_mass": 22
+			},
 			"temperature": 0,
 			"ramp": {
 				"rate": 5.0,