Make per-sensor weights visible and labelled in the zone form

Sensor weights already existed, but only as a second step after saving
a zone with two or more sensors, with fields labelled by raw keys such
as weight__sensor.living_a, so they were easy to miss.

The zone form now says that choosing two or more sensors leads to a
sensor-weight step. That step uses numbered fields ("Sensor 1 weight",
English and Romanian) and its description lists which sensor is which
by friendly name. Editing a multi-sensor zone shows the saved weights.
Stored data is unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

custom_components/heating_mpc/translations/en.json

@@ -143,7 +143,7 @@
       "step": {
         "user": {
           "title": "Thermal zone",
-          "description": "A room or area of the apartment. Sensor weights combine several sensors in one room; the comfort weight says how much the zone matters to the MPC. Neither changes the zone's learned thermal properties.",
+          "description": "A room or area of the apartment. Sensor weights combine several sensors in one room; the comfort weight says how much the zone matters to the MPC. Neither changes the zone's learned thermal properties. If you choose two or more sensors, the next step asks for each sensor's weight.",
           "data": {
             "name": "Name",
             "sensors": "Temperature sensors",
@@ -159,11 +159,19 @@
         },
         "sensor_weights": {
           "title": "Sensor weights",
-          "description": "How much each sensor counts in the zone temperature (0.1–10)."
+          "description": "How much each sensor counts in the zone temperature (0.1–10). Equal weights give the plain average.\n\n{sensors}",
+          "data": {
+            "sensor_weight_1": "Sensor 1 weight",
+            "sensor_weight_2": "Sensor 2 weight",
+            "sensor_weight_3": "Sensor 3 weight",
+            "sensor_weight_4": "Sensor 4 weight",
+            "sensor_weight_5": "Sensor 5 weight",
+            "sensor_weight_6": "Sensor 6 weight"
+          }
         },
         "reconfigure": {
           "title": "Thermal zone",
-          "description": "A room or area of the apartment. Sensor weights combine several sensors in one room; the comfort weight says how much the zone matters to the MPC. Neither changes the zone's learned thermal properties.",
+          "description": "A room or area of the apartment. Sensor weights combine several sensors in one room; the comfort weight says how much the zone matters to the MPC. Neither changes the zone's learned thermal properties. If you choose two or more sensors, the next step asks for each sensor's weight.",
           "data": {
             "name": "Name",
             "sensors": "Temperature sensors",