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.
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