Fix library batteries showing 0.0V

PocketBase stores battery nominal voltage in voltage_out while
voltage_in is 0.0 (not null). The nil-coalescing operator only
skips null, so 0.0 was returned instead of the real voltage.
Skip zero values when resolving displayVoltage on both platforms.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Cable/Loads/ComponentLibraryView.swift

@@ -24,7 +24,7 @@ struct ComponentLibraryItem: Identifiable, Equatable {
     let iconURL: URL?
 
     var displayVoltage: Double? {
-        voltageIn ?? voltageOut
+        [voltageIn, voltageOut].compactMap({ $0 }).first(where: { $0 > 0 })
     }
 
     var current: Double? {