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>

android/app/src/main/java/app/voltplan/cable/library/ComponentLibraryItem.kt

@@ -24,7 +24,7 @@ data class ComponentLibraryItem(
     val iconURL: String?,
     val affiliateLinks: List<AffiliateLink>,
 ) {
-    val displayVoltage: Double? get() = voltageIn ?: voltageOut
+    val displayVoltage: Double? get() = voltageIn?.takeIf { it > 0 } ?: voltageOut?.takeIf { it > 0 }
 
     val current: Double?
         get() {