fix harcoded altitude units

[MARMdeveloper]

Summary

Closes #195

Adds elevation unit conversion (meters ↔ feet) following the same logic as other units: if unit_of_length is mile, elevation is displayed in feet. Since TeslamateAPI does not convert elevation values, the conversion is implemented in UnitFormatter.

Changes

UnitFormatter

• Added formatElevation(value: Int?, units: Units?) — formats and converts meters to feet when imperial
• Added convertElevation(value: Float, units: Units?) — returns the numeric converted value for chart use
• Added getElevationUnit(units: Units?) — returns "ft" or "m" for chart axis label

DriveDetailScreen

• Replaced hardcoded "%,d m" in elevation stats (max, min, gain, loss) with UnitFormatter.formatElevation()
• Updated ElevationChartCard to use UnitFormatter.getElevationUnit() and UnitFormatter.convertElevation() via convertValue lambda

StatsScreen

• Replaced hardcoded "%,d m" in Records section (highest point, most climbing) with UnitFormatter.formatElevation()

DashboardScreen

• Replaced harcoded function with UnitFormatter.formatElevation()
• Fixed icon color to match accent color

[vide]

Rebased onto latest main and fixed two bugs:

• DriveDetailScreen: "Minimum" elevation stat was showing elevationMax instead of elevationMin (copy-paste error)
• StatsScreen: "Most Climbing" record lost its + prefix when switching to UnitFormatter.formatElevation()