fix: use composite key for CardInfo in HelpScreen grid

Multiple CardInfo entries can share the same nameRes (e.g., Troika has
both MifareClassic and MifareUltralight variants). Using nameRes.key
alone as the LazyVerticalGrid item key caused a duplicate key crash
when scrolling.

Add CardInfo.uniqueKey that combines nameRes.key with cardType.name,
and use it for grid keys and card selection in HelpScreen.

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

Author: Claude

app/src/commonMain/kotlin/com/codebutler/farebot/shared/ui/screen/HelpScreen.kt

@@ -280,14 +280,14 @@ fun ExploreContent(
                                 .padding(horizontal = 12.dp, vertical = 8.dp),
                     )
                 }
-                items(cards, key = { it.nameRes.key }) { card ->
+                items(cards, key = { it.uniqueKey }) { card ->
                     CardImageTile(
                         card = card,
                         cardName = cardNames[card.nameRes.key] ?: "",
                         isSupported = card.cardType in supportedCardTypes,
                         isKeysRequired = card.keysRequired && card.keyBundle !in loadedKeyBundles,
                         onTap = {
-                            selectedCardKey = card.nameRes.key
+                            selectedCardKey = card.uniqueKey
                         },
                     )
                 }
@@ -337,7 +337,7 @@ fun ExploreContent(
     // Bottom sheet for selected card details
     val selectedCard =
         selectedCardKey?.let { key ->
-            supportedCards.find { it.nameRes.key == key }
+            supportedCards.find { it.uniqueKey == key }
         }
     if (selectedCard != null) {
         ModalBottomSheet(

transit/src/commonMain/kotlin/com/codebutler/farebot/transit/CardInfo.kt

@@ -41,4 +41,6 @@ data class CardInfo(
     /** Brand color as 0xRRGGBB (no alpha). Null if unknown — UI will use a theme-appropriate fallback. */
     val brandColor: Int?,
     val credits: List<String> = emptyList(),
-)
+) {
+    val uniqueKey: String get() = "${nameRes.key}:${cardType.name}"
+}