refactor: consolidate metric formatting through MetricFormatter

Replace 11 inline formatString("%.Nf ...") metric display calls with
MetricFormatter helpers in core/common. Adds two new helpers (windSpeed,
rainfall) for m/s and mm readings.

Migrated (11 sites):
- feature/node EnvironmentMetrics.kt: humidity, pressure, voltage,
  current, wind_speed, wind_gust, wind_lull, rainfall_1h, rainfall_24h
- feature/settings LoadingOverlay.kt, PacketResponseStateDialog.kt:
  progress percent indicators

New helpers in MetricFormatter:
- windSpeed(metersPerSecond, decimalPlaces = 1) -> "X.X m/s"
- rainfall(millimeters, decimalPlaces = 1) -> "X.X mm"

Intentionally left alone:
- core/model DistanceExtensions.kt: specialized unit-conversion helpers,
  which are themselves the canonical distance/speed formatters
- feature/node PositionLogComponents.kt, MetricsViewModel.kt: GPS
  coordinates and heading-angle formatters (not metric display strings)
- feature/node TracerouteChart, HostMetricsChart, EnvironmentCharts,
  PaxMetrics valueFormatter lambdas: chart-library axis callbacks with
  format strings scoped to the chart lib contract
- feature/node TracerouteLog.kt, HostMetricsLog.kt: generic
  "label: value" log rows, not metric displays
- feature/node CompassBottomSheet.kt: one-off %.0f° angle
- EnvironmentMetrics.kt lux, UV-lux, gas resistance, radiation, and
  wind-with-direction formats: one-off specialized units not worth a
  dedicated helper

Also adds detekt @Suppress("TooManyFunctions") on MetricFormatter
(11 helpers now exceeds the default threshold) and unit tests for the
new windSpeed/rainfall helpers.

Validation: ./gradlew spotlessApply, :core:common:jvmTest,
:core:common:detekt, spotlessCheck, and kmpSmokeCompile all pass.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

core/common/src/commonMain/kotlin/org/meshtastic/core/common/util/MetricFormatter.kt

@@ -23,6 +23,7 @@ package org.meshtastic.core.common.util
  * All methods return locale-independent strings using [NumberFormatter] (dot decimal separator), which is intentional
  * for a mesh networking app where consistency matters.
  */
+@Suppress("TooManyFunctions")
 object MetricFormatter {
 
     fun temperature(celsius: Float, isFahrenheit: Boolean): String {
@@ -47,6 +48,12 @@ object MetricFormatter {
     fun snr(value: Float, decimalPlaces: Int = 1): String = "${NumberFormatter.format(value, decimalPlaces)} dB"
 
     fun rssi(value: Int): String = "$value dBm"
+
+    fun windSpeed(metersPerSecond: Float, decimalPlaces: Int = 1): String =
+        "${NumberFormatter.format(metersPerSecond, decimalPlaces)} m/s"
+
+    fun rainfall(millimeters: Float, decimalPlaces: Int = 1): String =
+        "${NumberFormatter.format(millimeters, decimalPlaces)} mm"
 }
 
 private const val FAHRENHEIT_SCALE = 1.8f

core/common/src/commonTest/kotlin/org/meshtastic/core/common/util/MetricFormatterTest.kt

@@ -120,4 +120,24 @@ class MetricFormatterTest {
     fun snrNegative() {
         assertEquals("-5.5 dB", MetricFormatter.snr(-5.5f))
     }
+
+    @Test
+    fun windSpeed() {
+        assertEquals("12.3 m/s", MetricFormatter.windSpeed(12.34f))
+    }
+
+    @Test
+    fun windSpeedZero() {
+        assertEquals("0.0 m/s", MetricFormatter.windSpeed(0.0f))
+    }
+
+    @Test
+    fun rainfall() {
+        assertEquals("2.5 mm", MetricFormatter.rainfall(2.54f))
+    }
+
+    @Test
+    fun rainfallZero() {
+        assertEquals("0.0 mm", MetricFormatter.rainfall(0.0f))
+    }
 }