feat v1.31.0: room cards — metrics line + proportional resize

- room label becomes a card: name on top, optional metrics below
  (temperature / humidity / avg zigbee / lights), four checkboxes in
  space settings, all off by default; lights render On/Off or '1 of 3'
- areaHum + areaLightStats pure helpers (+3 unit tests, 90 total)
- resize via corner handles in the Plan editor (hover), uniform 0.5-3x,
  scale stored as layout k next to the position; drag preserves it
- fix latent v1.25 regression: draggable HTML labels were never rendered
  in the Plan editor (static SVG only) — real name-only cards now render
  there, draggable and resizable
- repair merge/split smokes still calling removed _toggleMarkup
- validation.py: 4 label_* bools; smoke_room_cards.mjs; docs same-commit

src/i18n/en.json

@@ -252,5 +252,13 @@
   "devbar.add": "Add",
   "devbar.show_all": "Show all",
   "devbar.reset": "Reset",
-  "devbar.rules": "Icon rules"
+  "devbar.rules": "Icon rules",
+  "space.roomcard_section": "Room card shows:",
+  "space.label_temp": "Temperature",
+  "space.label_hum": "Humidity",
+  "space.label_lqi": "Average Zigbee signal",
+  "space.label_light": "Lights on/off",
+  "roomcard.light_on": "On",
+  "roomcard.light_off": "Off",
+  "roomcard.light_partial": "{on} of {total}"
 }