feat(environment): add 1-Wire multi-thermometer (DS18B20) display support

Add charting, detail card display, and CSV export for up to 8 1-Wire
temperature sensor channels from the environment_metrics.one_wire_temperature
repeated field.

- EnvironmentMetricsState: ONE_WIRE_TEMP_1..8 enum entries with getOrNull()
  access (safely returns null when firmware does not populate the field)
- EnvironmentCharts: LEGEND_DATA_4 with per-channel labels and distinct colours
- CommonCharts: LegendData.labelOverride for per-instance legend labels
- EnvironmentMetrics: OneWireTemperatureDisplay composable in the detail card
- EnvironmentMetrics component: inline 1-Wire chip display with temp formatting
- MetricsViewModel: Fahrenheit conversion for one_wire_temperature in CSV export

No version gating needed — the proto field defaults to an empty list on older
firmware, so the UI elements are naturally hidden when no data is reported.

core/ui/src/commonMain/kotlin/org/meshtastic/core/ui/theme/CustomColors.kt

@@ -60,6 +60,10 @@ object GraphColors {
     val Lime = Color(0xFFCDDC39)
     val Indigo = Color(0xFF3F51B5)
     val DeepOrange = Color(0xFFFF5722)
+    val Magenta = Color(0xFFE040FB)
+    val SkyBlue = Color(0xFF03A9F4)
+    val Chartreuse = Color(0xFF76FF03)
+    val Coral = Color(0xFFFF6E40)
 }
 
 object StatusColors {