Wall metadata panel ignores imperial unit setting

[MateoSaettone]

Problem

When the viewer unit is switched to imperial, wall drawing labels render in feet/inches, but the selected wall metadata panel still displays editable dimensions in meters.

In imperial mode, the toolbar is set to ft, but the selected wall metadata panel still displays metric values.

Expected

Wall metadata dimensions should follow the active viewer unit. In imperial mode, editable numeric controls should display feet while still persisting scene values internally in meters.

Scope

• Wall metadata panel length, height, thickness, and curve controls
• Shared linear measurement formatting/conversion helpers so wall labels and related measurement labels do not duplicate imperial formatting logic

Verification

This is covered by draft PR #321.