The tab bar floated mid-screen, and the Account tab could not be reached

Found by opening the two tabs nothing had ever opened.

⚠️ **The tab bar was not pinned.** It and the screen content were plain
siblings in a Column with no weight between them, so the bar sat immediately
under whatever had been drawn: near the TOP of an empty Alerts tab, above a
screen of blank, which reads as a broken layout rather than as an empty state.

🔴 **On the Account tab it was pushed off the bottom entirely, and the screen
could not scroll.** Account is taller than the viewport, so the sign-out
explanation was unreadable and there was no way to switch tabs from it at all.

The content area now takes the weight and the bar sits below it. ⚠️ Only the
screens WITHOUT a lazy list scroll — Contacts owns a LazyColumn, and a lazy
list inside a vertically scrolling Column is measured with infinite height and
crashes outright, which is what the comment there has always warned about.

⚠️ Not a bug, for whoever sees it next: "Flamenet Messenger isn't responding"
on the emulator during this work was the SYSTEM starving, not the app. The ANR
reason names `Taskbar (server) is not responding, waited 33979ms` with the host
at load 35. The app's own restore does its network work inside
`withContext(Dispatchers.IO)`; it was not blocking the main thread.

⚠️ Also seen and left alone: the group row shows "You, user 32" for a few
seconds after a cold start, because the buddy list has not loaded yet and the
fallback prints the raw id. It corrects itself once buddies arrive. Naming it
properly would mean carrying member handles on the group record, which the
relay does not send today.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

app/src/main/kotlin/io/flamenet/messenger/app/MainActivity.kt

@@ -95,11 +95,38 @@ private fun Root(model: MessengerViewModel = viewModel()) {
                     if (chat != null) {
                         ChatScreen(model, chat, current.error, current.buddies)
                     } else {
-                        when (current.screen) {
-                            MessengerViewModel.Phase.Screen.CONTACTS -> SignedIn(model, current)
-                            MessengerViewModel.Phase.Screen.NOTIFICATIONS ->
-                                NotificationsScreen(model, current)
-                            MessengerViewModel.Phase.Screen.ACCOUNT -> AccountScreen(model, current)
+                        // 🔴 **The content area is weighted, and the tab bar is
+                        // not.** These used to be plain siblings, so the tab bar
+                        // sat immediately under whatever the screen had drawn:
+                        // near the TOP of an empty Alerts tab, and pushed clean
+                        // OFF the bottom by the Account tab, which is taller
+                        // than the screen. Account also could not scroll, so the
+                        // sign-out explanation was unreadable and there was no
+                        // way back to another tab.
+                        //
+                        // ⚠️ Only the screens WITHOUT a lazy list may scroll.
+                        // Contacts owns a LazyColumn, and a lazy list inside a
+                        // vertically scrolling Column is measured with infinite
+                        // height and crashes outright.
+                        Column(
+                            modifier = Modifier
+                                .weight(1f)
+                                .then(
+                                    if (current.screen == MessengerViewModel.Phase.Screen.CONTACTS) {
+                                        Modifier
+                                    } else {
+                                        Modifier.verticalScroll(rememberScrollState())
+                                    }
+                                ),
+                            verticalArrangement = Arrangement.spacedBy(12.dp),
+                        ) {
+                            when (current.screen) {
+                                MessengerViewModel.Phase.Screen.CONTACTS -> SignedIn(model, current)
+                                MessengerViewModel.Phase.Screen.NOTIFICATIONS ->
+                                    NotificationsScreen(model, current)
+                                MessengerViewModel.Phase.Screen.ACCOUNT ->
+                                    AccountScreen(model, current)
+                            }
                         }
                         BottomNav(model, current)
                     }