UI: lists in grouped surface cards; debug demo seeder

- Per-account lists now render inside rounded surfaceContainer cards
  (grouped-list pattern) with inset dividers and transparent rows, instead
  of bare ListItems on the background — surfaces-first per design feedback.
- Add debug-only DemoSeeder (local, non-syncing 'Floret Demo' list) behind
  BuildConfig.DEBUG + an intent extra, to populate the UI for design review.

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

app/src/main/java/de/jeanlucmakiola/floret/MainActivity.kt

@@ -12,11 +12,15 @@ import androidx.compose.runtime.getValue
 import androidx.compose.ui.Modifier
 import androidx.hilt.navigation.compose.hiltViewModel
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import androidx.lifecycle.lifecycleScope
 import dagger.hilt.android.AndroidEntryPoint
+import de.jeanlucmakiola.floret.data.demo.DemoSeeder
 import de.jeanlucmakiola.floret.data.prefs.ThemeMode
 import de.jeanlucmakiola.floret.ui.RootScreen
 import de.jeanlucmakiola.floret.ui.settings.SettingsViewModel
 import de.jeanlucmakiola.floret.ui.theme.FloretTheme
+import kotlinx.coroutines.launch
+import javax.inject.Inject
 
 /**
  * Single activity. The theme follows [SettingsViewModel]; [RootScreen] is the
@@ -26,9 +30,17 @@ import de.jeanlucmakiola.floret.ui.theme.FloretTheme
 @AndroidEntryPoint
 class MainActivity : ComponentActivity() {
 
+    @Inject lateinit var demoSeeder: DemoSeeder
+
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         enableEdgeToEdge()
+
+        // Debug-only sample data: `am start ... --ez floret_seed true`. Seeds a
+        // local (non-syncing) demo list once; no-op without the extra.
+        if (BuildConfig.DEBUG && intent.getBooleanExtra(EXTRA_SEED, false)) {
+            lifecycleScope.launch { runCatching { demoSeeder.seed() } }
+        }
         setContent {
             val settingsViewModel: SettingsViewModel = hiltViewModel()
             val ui by settingsViewModel.state.collectAsStateWithLifecycle()
@@ -45,6 +57,7 @@ class MainActivity : ComponentActivity() {
 
     companion object {
         const val EXTRA_TASK_ID = "de.jeanlucmakiola.floret.extra.TASK_ID"
+        private const val EXTRA_SEED = "floret_seed"
 
         /** Opens the app focused on a task (reminder taps). Routing lands with the UI. */
         fun taskIntent(context: Context, taskId: Long): Intent =

app/src/main/java/de/jeanlucmakiola/floret/data/demo/DemoSeeder.kt

@@ -0,0 +1,60 @@
+package de.jeanlucmakiola.floret.data.demo
+
+import de.jeanlucmakiola.floret.data.di.IoDispatcher
+import de.jeanlucmakiola.floret.data.tasks.TasksRepository
+import de.jeanlucmakiola.floret.domain.DayWindow
+import de.jeanlucmakiola.floret.domain.Priority
+import de.jeanlucmakiola.floret.domain.TaskForm
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.withContext
+import java.time.ZoneId
+import javax.inject.Inject
+import javax.inject.Singleton
+import kotlin.time.Clock
+import kotlin.time.Instant
+
+/**
+ * Debug-only one-shot sample data. Creates a **local, device-only** list
+ * ("Floret Demo") — so nothing syncs to a CalDAV server — and fills it with
+ * tasks spread across overdue / today / upcoming / no-date / completed so every
+ * smart list shows content. Idempotent: skips if the demo list already exists.
+ * Triggered from [de.jeanlucmakiola.floret.MainActivity] only in debug builds.
+ */
+@Singleton
+class DemoSeeder @Inject constructor(
+    private val repository: TasksRepository,
+    @IoDispatcher private val io: CoroutineDispatcher,
+) {
+    suspend fun seed(): Unit = withContext(io) {
+        val lists = runCatching { repository.taskLists().first() }.getOrElse { return@withContext }
+        if (lists.any { it.name == DEMO_LIST && it.isLocal }) return@withContext
+
+        val listId = runCatching { repository.createLocalList(DEMO_LIST, DEMO_COLOR) }
+            .getOrElse { return@withContext }
+
+        val (todayStart, todayEnd) = DayWindow.today(Clock.System.now(), ZoneId.systemDefault())
+        val ts = todayStart.toEpochMilliseconds()
+        val te = todayEnd.toEpochMilliseconds()
+        val hour = 3_600_000L
+        val day = 86_400_000L
+        fun at(millis: Long): Instant = Instant.fromEpochMilliseconds(millis)
+
+        repository.createTask(TaskForm(title = "Water the office plants", listId = listId, due = at(ts - hour), priority = Priority.HIGH))
+        repository.createTask(TaskForm(title = "Reply to client email", listId = listId, due = at(te - 2 * hour), priority = Priority.MEDIUM))
+        repository.createTask(TaskForm(title = "Write stand-up notes", listId = listId, due = at(te - hour)))
+        val invoiceId = repository.createTask(TaskForm(title = "Prepare monthly invoice", listId = listId, due = at(te + 2 * day), priority = Priority.MEDIUM))
+        repository.createTask(TaskForm(title = "Gather receipts", listId = listId, parentId = invoiceId))
+        repository.createTask(TaskForm(title = "Book train tickets", listId = listId, due = at(te + 6 * day), priority = Priority.LOW))
+        repository.createTask(TaskForm(title = "Read Compose 1.5 release notes", listId = listId))
+        repository.createTask(TaskForm(title = "Sketch the Floret app icon", listId = listId))
+
+        val done = repository.createTask(TaskForm(title = "Renew domain name", listId = listId, due = at(ts - 2 * day)))
+        repository.setCompleted(done, completed = true)
+    }
+
+    private companion object {
+        const val DEMO_LIST = "Floret Demo"
+        const val DEMO_COLOR = 0xFF7A5C6B.toInt()
+    }
+}

app/src/main/java/de/jeanlucmakiola/floret/ui/lists/ListsScreen.kt

@@ -14,21 +14,24 @@ import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.lazy.LazyColumn
-import androidx.compose.foundation.lazy.items
 import androidx.compose.foundation.shape.CircleShape
+import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.automirrored.rounded.ListAlt
 import androidx.compose.material.icons.rounded.Add
 import androidx.compose.material.icons.rounded.ErrorOutline
 import androidx.compose.material.icons.rounded.Today
 import androidx.compose.material.icons.rounded.Upcoming
+import androidx.compose.material3.Card
 import androidx.compose.material3.CardDefaults
 import androidx.compose.material3.ElevatedCard
 import androidx.compose.material3.ExperimentalMaterial3Api
 import androidx.compose.material3.ExtendedFloatingActionButton
+import androidx.compose.material3.HorizontalDivider
 import androidx.compose.material3.Icon
 import androidx.compose.material3.LargeTopAppBar
 import androidx.compose.material3.ListItem
+import androidx.compose.material3.ListItemDefaults
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Scaffold
 import androidx.compose.material3.Text
@@ -111,9 +114,8 @@ private fun ListsContent(
         } else {
             item { SectionHeader(stringResource(R.string.lists_header)) }
             state.groups.forEach { group ->
-                item(key = "acct-${group.accountName}") { AccountHeader(group.accountName) }
-                items(group.lists, key = { it.list.id }) { overview ->
-                    ListRow(overview) { onOpenFilter(TaskFilter.OfList(overview.list.id)) }
+                item(key = "acct-${group.accountName}") {
+                    AccountGroupCard(group, onOpenFilter)
                 }
             }
         }
@@ -178,10 +180,36 @@ private fun SmartCard(count: SmartCount, modifier: Modifier = Modifier, onClick:
     }
 }
 
+/** One account's lists as a single rounded surface card (grouped-list pattern). */
+@Composable
+private fun AccountGroupCard(group: AccountGroup, onOpenFilter: (TaskFilter) -> Unit) {
+    Column(Modifier.padding(horizontal = 16.dp)) {
+        AccountHeader(group.accountName)
+        Card(
+            modifier = Modifier.fillMaxWidth(),
+            shape = RoundedCornerShape(20.dp),
+            colors = CardDefaults.cardColors(
+                containerColor = MaterialTheme.colorScheme.surfaceContainer,
+            ),
+        ) {
+            group.lists.forEachIndexed { index, overview ->
+                ListRow(overview) { onOpenFilter(TaskFilter.OfList(overview.list.id)) }
+                if (index < group.lists.lastIndex) {
+                    HorizontalDivider(
+                        color = MaterialTheme.colorScheme.outlineVariant,
+                        modifier = Modifier.padding(start = 56.dp),
+                    )
+                }
+            }
+        }
+    }
+}
+
 @Composable
 private fun ListRow(overview: ListOverview, onClick: () -> Unit) {
     ListItem(
         modifier = Modifier.clickable(onClick = onClick),
+        colors = ListItemDefaults.colors(containerColor = Color.Transparent),
         leadingContent = { ColorDot(overview.list.color) },
         headlineContent = { Text(overview.list.name) },
         trailingContent = {
@@ -222,7 +250,7 @@ private fun AccountHeader(text: String) {
         text = text,
         style = MaterialTheme.typography.labelLarge,
         color = MaterialTheme.colorScheme.onSurfaceVariant,
-        modifier = Modifier.padding(start = 16.dp, end = 16.dp, top = 8.dp, bottom = 4.dp),
+        modifier = Modifier.padding(start = 4.dp, top = 12.dp, bottom = 6.dp),
     )
 }