Add onboarding image carousel

Bundle the rotating onboarding illustrations (light/dark) and wire them
into the Android onboarding info component, matching the iOS carousel.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

android/app/src/main/java/app/voltplan/cable/ui/components/OnboardingCarousel.kt

@@ -0,0 +1,59 @@
+package app.voltplan.cable.ui.components
+
+import androidx.annotation.DrawableRes
+import androidx.compose.animation.AnimatedContent
+import androidx.compose.animation.core.tween
+import androidx.compose.animation.slideInHorizontally
+import androidx.compose.animation.slideOutHorizontally
+import androidx.compose.animation.togetherWith
+import androidx.compose.foundation.Image
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableIntStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.layout.ContentScale
+import androidx.compose.ui.res.painterResource
+import kotlinx.coroutines.delay
+
+/**
+ * Auto-advancing onboarding illustration carousel. Mirrors iOS `OnboardingCarouselView`:
+ * cycles through the images every 8s with a horizontal slide. A single image stays static.
+ */
+@Composable
+fun OnboardingCarousel(
+    @DrawableRes images: List<Int>,
+    modifier: Modifier = Modifier,
+) {
+    if (images.isEmpty()) return
+    var index by remember(images) { mutableIntStateOf(0) }
+
+    if (images.size > 1) {
+        LaunchedEffect(images) {
+            while (true) {
+                delay(8_000)
+                index = (index + 1) % images.size
+            }
+        }
+    }
+
+    AnimatedContent(
+        targetState = index,
+        transitionSpec = {
+            slideInHorizontally(tween(800)) { it } togetherWith
+                slideOutHorizontally(tween(800)) { -it }
+        },
+        label = "onboarding-carousel",
+        modifier = modifier,
+    ) { i ->
+        Image(
+            painter = painterResource(images[i]),
+            contentDescription = null,
+            contentScale = ContentScale.Fit,
+            modifier = Modifier.fillMaxSize(),
+        )
+    }
+}

android/app/src/main/java/app/voltplan/cable/ui/components/OnboardingInfo.kt

@@ -1,10 +1,12 @@
 package app.voltplan.cable.ui.components
 
+import androidx.annotation.DrawableRes
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.size
 import androidx.compose.material3.Button
@@ -29,6 +31,7 @@ fun OnboardingInfo(
     onPrimary: () -> Unit,
     secondaryLabel: String? = null,
     onSecondary: (() -> Unit)? = null,
+    @DrawableRes images: List<Int> = emptyList(),
     modifier: Modifier = Modifier,
 ) {
     Column(
@@ -36,7 +39,11 @@ fun OnboardingInfo(
         horizontalAlignment = Alignment.CenterHorizontally,
         verticalArrangement = Arrangement.Center,
     ) {
-        Icon(icon, contentDescription = null, tint = MaterialTheme.colorScheme.primary, modifier = Modifier.size(56.dp))
+        if (images.isNotEmpty()) {
+            OnboardingCarousel(images = images, modifier = Modifier.fillMaxWidth().height(200.dp))
+        } else {
+            Icon(icon, contentDescription = null, tint = MaterialTheme.colorScheme.primary, modifier = Modifier.size(56.dp))
+        }
         Spacer(Modifier.size(16.dp))
         Text(title, style = MaterialTheme.typography.titleLarge, textAlign = TextAlign.Center)
         Spacer(Modifier.size(8.dp))