fix: preserve bottom-tab state during tab switching

Restore top-level tab destinations instead of recreating them on each tap, and avoid immediately resubscribing inbox streams when users bounce between tabs. This reduces navigation jank and repeated hangs on slower devices.

app/src/main/kotlin/com/wisp/app/Navigation.kt

@@ -1,5 +1,6 @@
 package com.wisp.app
 
+import android.os.SystemClock
 import androidx.activity.compose.BackHandler
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
@@ -26,6 +27,7 @@ import androidx.lifecycle.Lifecycle
 import androidx.lifecycle.LifecycleEventObserver
 import androidx.lifecycle.viewmodel.compose.viewModel
 import androidx.navigation.NavType
+import androidx.navigation.NavGraph.Companion.findStartDestination
 import androidx.navigation.compose.NavHost
 import androidx.navigation.compose.composable
 import androidx.navigation.compose.currentBackStackEntryAsState
@@ -527,6 +529,16 @@ fun WispNavHost(
         }
     }
 
+    var lastInboxRefreshElapsedMs by rememberSaveable { mutableLongStateOf(0L) }
+    fun refreshInboxSubscriptionsIfStale() {
+        val now = SystemClock.elapsedRealtime()
+        // Inbox subscriptions already stay live in the background; avoid re-sending the
+        // same REQs every time the user bounces between top-level tabs.
+        if (now - lastInboxRefreshElapsedMs < 30_000L) return
+        lastInboxRefreshElapsedMs = now
+        feedViewModel.refreshDmsAndNotifications()
+    }
+
     // Crash report dialog — check on launch if a crash log exists
     var showCrashDialog by remember { mutableStateOf(CrashHandler.hasCrashLog(context)) }
     if (showCrashDialog) {
@@ -607,8 +619,11 @@ fun WispNavHost(
                             } else {
                                 if (tab == BottomTab.WALLET) walletViewModel.navigateHome()
                                 navController.navigate(tab.route) {
-                                    popUpTo(Routes.FEED) { inclusive = false }
+                                    popUpTo(navController.graph.findStartDestination().id) {
+                                        saveState = true
+                                    }
                                     launchSingleTop = true
+                                    restoreState = true
                                 }
                             }
                         }
@@ -1271,7 +1286,7 @@ fun WispNavHost(
 
         composable(Routes.DM_LIST) {
             LaunchedEffect(Unit) {
-                feedViewModel.refreshDmsAndNotifications()
+                refreshInboxSubscriptionsIfStale()
                 // Decrypt pending gift wraps when signer is available
                 activeSigner?.let { dmListViewModel.decryptPending(it) }
                 dmListViewModel.markDmsRead()
@@ -1331,7 +1346,7 @@ fun WispNavHost(
             val dmConvoViewModel: DmConversationViewModel = viewModel()
             val userPubkey = feedViewModel.getUserPubkey()
             LaunchedEffect(pubkey) {
-                feedViewModel.refreshDmsAndNotifications()
+                refreshInboxSubscriptionsIfStale()
                 dmConvoViewModel.init(
                     peerPubkeyHex = pubkey,
                     dmRepository = feedViewModel.dmRepo,
@@ -1413,7 +1428,7 @@ fun WispNavHost(
             val dmConvoViewModel: DmConversationViewModel = viewModel()
             val userPubkey = feedViewModel.getUserPubkey()
             LaunchedEffect(convKey) {
-                feedViewModel.refreshDmsAndNotifications()
+                refreshInboxSubscriptionsIfStale()
                 dmConvoViewModel.init(
                     peerPubkeyHex = participantList.firstOrNull() ?: "",
                     dmRepository = feedViewModel.dmRepo,
@@ -3034,7 +3049,7 @@ fun WispNavHost(
                 onDispose { feedViewModel.notifRepo.isViewing = false }
             }
             LaunchedEffect(Unit) {
-                feedViewModel.refreshDmsAndNotifications()
+                refreshInboxSubscriptionsIfStale()
                 notificationsViewModel.markRead()
             }