fix(conversations): don't re-restore the scroll position on every resume

Returning from a chat to the conversation list made the list visibly
jump shortly after rendering. The saved scroll position was re-armed on
every resume and restored on the next room list emission - which used
to be an immediate local snapshot, making the restore an invisible
no-op. With the list derived reactively from the database, the state
current at resume never re-emits, so the first post-resume emission is
the server sync response seconds later: scrollToItem then re-anchored
an already rendered (and possibly slightly changed) list under the
user's eyes.

Restore the position only once per activity lifetime: after a
recreation the LazyListState is genuinely lost and the first emission -
which the reactive flow now delivers immediately on subscription -
restores it, while a plain resume keeps the retained state's position
naturally, without any late scrollToItem.

Assisted-by: Claude Code:claude-fable-5
Signed-off-by: Andy Scherzinger <info@andy-scherzinger.de>

Author: AndyScherzinger

app/src/main/java/com/nextcloud/talk/conversationlist/ConversationsListActivity.kt

@@ -160,7 +160,7 @@ class ConversationsListActivity : BaseActivity() {
     // Lazy list state – set from inside setContent, read from onPause
     private var conversationListLazyListState: androidx.compose.foundation.lazy.LazyListState? = null
 
-    // Ensures saved scroll position is restored only once per resume cycle, not on every room-list refresh.
+    // restored once per activity lifetime; a late scrollToItem on resume would jump the rendered list
     private var scrollPositionRestored = false
 
     private var nextUnreadConversationScrollPosition = 0
@@ -385,7 +385,6 @@ class ConversationsListActivity : BaseActivity() {
 
     override fun onResume() {
         super.onResume()
-        scrollPositionRestored = false
 
         showNotificationWarningState.value = shouldShowNotificationWarning()
         showShareToScreenState.value = hasActivityActionSendIntent()