Update clients, docs, and install for CarConnectivity migration

- gui_client: update _TRACE_LABELS paths to new flat snapshot structure
- README: update library name, pip command, domain list, credentials
  template, output example, and module reference
- install.sh: update credentials template and systemd service description
- client.py: update docstring
- data_model: Kelvin→Celsius conversion for battery temps (CarConnectivity
  returns Kelvin); round range_estimated_full to 1 decimal
- jay_diff: fix merge when old value is not a dict; skip empty-dict
  branches in delete

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

gui_client.py

@@ -94,20 +94,19 @@ _SETTINGS_PATH   = Path.home() / ".config" / "we_monitor" / "plot_settings.json"
 # Maps full dotted trace key → short display label used in chips, legends and
 # cursor readout.  Falls back to the last path component for unknown keys.
 _TRACE_LABELS: dict[str, str] = {
-    "charging.chargingStatus.chargePower":                           "charge power",
-    "charging.chargingStatus.remainingChargingTimeToComplete":       "time to full",
-    "charging.batteryStatus.currentSOC":                             "SOC",
-    "charging.batteryStatus.cruisingRangeElectric":                  "range",
-    "charging.chargingSettings.targetSOC":                           "target SOC",
-    "climatisation.climatisationStatus.remainingClimatisationTime":  "clim. time",
-    "climatisation.climatisationSettings.targetTemperature":         "target temp",
-    "measurements.odometerStatus.odometer":                          "odometer",
-    "measurements.rangeStatus.electricRange":                        "elec. range",
-    "measurements.rangeStatus.totalRange":                           "total range",
-    "measurements.temperatureBatteryStatus.temperatureHvBatteryMax": "batt. temp max",
-    "measurements.temperatureBatteryStatus.temperatureHvBatteryMin": "batt. temp min",
-    "measurements.temperatureOutsideStatus.temperatureOutside":      "outside temp",
-    "procedural.range_at_100":                                       "range 100%"
+    "charging.power":                                "charge power",
+    "charging.remain":                               "time to full",
+    "charging.settings.target_level":               "target SOC",
+    "climatisation.remain":                          "clim. time",
+    "climatisation.settings.target_temperature":     "target temp",
+    "climatisation.environment.temperature_outside": "outside temp",
+    "electric_drive.battery.soc":                    "SOC",
+    "electric_drive.range":                          "range",
+    "electric_drive.range_full":                     "range (full)",
+    "electric_drive.battery.temperature_max":        "batt. temp max",
+    "electric_drive.battery.temperature_min":        "batt. temp min",
+    "electric_drive.odometer.odometer":              "odometer",
+    "procedural.range_at_100":                       "range 100%",
 }