feat: add staggered card entrance animation in feed

app/src/main/java/com/swoosh/microblog/ui/feed/FeedScreen.kt

@@ -9,6 +9,8 @@ import androidx.compose.animation.animateColorAsState
 import androidx.compose.animation.core.animateFloatAsState
 import androidx.compose.animation.fadeIn
 import androidx.compose.animation.fadeOut
+import androidx.compose.animation.slideInVertically
+import kotlinx.coroutines.delay
 import androidx.compose.foundation.gestures.detectTapGestures
 import com.swoosh.microblog.ui.animation.SwooshMotion
 import androidx.compose.foundation.ExperimentalFoundationApi
@@ -115,6 +117,10 @@ fun FeedScreen(
     var showDeleteConfirmation by remember { mutableStateOf<GhostAccount?>(null) }
     var showRenameDialog by remember { mutableStateOf<GhostAccount?>(null) }
 
+    // Staggered entrance tracking
+    val animatedKeys = remember { mutableStateMapOf<String, Boolean>() }
+    var initialLoadComplete by remember { mutableStateOf(false) }
+
     // FAB entrance animation
     var fabVisible by remember { mutableStateOf(false) }
     val fabScale by animateFloatAsState(
@@ -471,6 +477,12 @@ fun FeedScreen(
                         if (isSearchActive && searchQuery.isNotBlank()) {
                             // Search results: flat list with highlighting, no swipe actions
                             items(displayPosts, key = { it.ghostId ?: "local_${it.localId}" }) { post ->
+                                val itemKey = post.ghostId ?: "local_${post.localId}"
+                                StaggeredItem(
+                                    key = itemKey,
+                                    animatedKeys = animatedKeys,
+                                    initialLoadComplete = initialLoadComplete
+                                ) {
                                     PostCard(
                                         post = post,
                                         onClick = { onPostClick(post) },
@@ -478,11 +490,18 @@ fun FeedScreen(
                                         highlightQuery = searchQuery
                                     )
                                 }
+                            }
                         } else {
                             // Normal feed: pinned section + swipe actions
                             // Pinned posts (no section header — pin icon on post)
                             if (pinnedPosts.isNotEmpty()) {
                                 items(pinnedPosts, key = { "pinned_${it.ghostId ?: "local_${it.localId}"}" }) { post ->
+                                    val itemKey = post.ghostId ?: "local_${post.localId}"
+                                    StaggeredItem(
+                                        key = itemKey,
+                                        animatedKeys = animatedKeys,
+                                        initialLoadComplete = initialLoadComplete
+                                    ) {
                                         SwipeablePostCard(
                                             post = post,
                                             onClick = { onPostClick(post) },
@@ -512,10 +531,17 @@ fun FeedScreen(
                                             snackbarHostState = snackbarHostState
                                         )
                                     }
+                                }
                                 // No extra separator — thick dividers built into each post
                             }
 
                             items(regularPosts, key = { it.ghostId ?: "local_${it.localId}" }) { post ->
+                                val itemKey = post.ghostId ?: "local_${post.localId}"
+                                StaggeredItem(
+                                    key = itemKey,
+                                    animatedKeys = animatedKeys,
+                                    initialLoadComplete = initialLoadComplete
+                                ) {
                                     SwipeablePostCard(
                                         post = post,
                                         onClick = { onPostClick(post) },
@@ -546,6 +572,7 @@ fun FeedScreen(
                                     )
                                 }
                             }
+                        }
 
                         if (!isSearchActive && state.isLoadingMore) {
                             item {
@@ -559,6 +586,13 @@ fun FeedScreen(
                         }
                     }
 
+                    LaunchedEffect(state.posts) {
+                        if (state.posts.isNotEmpty() && !initialLoadComplete) {
+                            delay(SwooshMotion.StaggerDelayMs * minOf(state.posts.size, 8) + 300)
+                            initialLoadComplete = true
+                        }
+                    }
+
                     if (!isSearchActive) {
                         PullRefreshIndicator(
                             refreshing = state.isRefreshing,
@@ -707,6 +741,35 @@ fun FeedScreen(
     }
 }
 
+@Composable
+private fun StaggeredItem(
+    key: String,
+    animatedKeys: MutableMap<String, Boolean>,
+    initialLoadComplete: Boolean,
+    content: @Composable () -> Unit
+) {
+    val shouldAnimate = !initialLoadComplete && key !in animatedKeys
+    var visible by remember { mutableStateOf(!shouldAnimate) }
+
+    LaunchedEffect(key) {
+        if (shouldAnimate && animatedKeys.size < 8) {
+            delay(SwooshMotion.StaggerDelayMs * animatedKeys.size)
+            animatedKeys[key] = true
+        }
+        visible = true
+    }
+
+    AnimatedVisibility(
+        visible = visible,
+        enter = slideInVertically(
+            initialOffsetY = { it / 3 },
+            animationSpec = SwooshMotion.gentle()
+        ) + fadeIn(animationSpec = SwooshMotion.quick())
+    ) {
+        content()
+    }
+}
+
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
 fun FilterChipsBar(