Long-press blanks screen unless actively browsing a list

Contacts/Messages/Nodes screens consumed long-press as soon as they
loaded, which surfaced delete/menu dialogs instead of blanking the
display. Gate per-screen long-press consumption on _focusActive so the
delete affordance only fires after the user has navigated into the
list with up/down/enter. From the resting tab view, long-press falls
through to main.cpp and powers the screen off — same behaviour as the
home screen.

src/ui/screens/LvContactsScreen.cpp

@@ -119,6 +119,9 @@ void LvContactsScreen::rebuildList() {
 
 bool LvContactsScreen::handleLongPress() {
     if (!_am || _contactIndices.empty()) return false;
+    // Only consume long-press once the user has actively navigated into
+    // the list. Otherwise let main.cpp blank the screen.
+    if (!_focusActive) return false;
     lv_obj_t* focused = lv_group_get_focused(LvInput::group());
     if (!focused) return false;
     _deleteIdx = (int)(intptr_t)lv_obj_get_user_data(focused);

src/ui/screens/LvMessagesScreen.cpp

@@ -185,6 +185,9 @@ int LvMessagesScreen::getFocusedPeerIdx() const {
 
 bool LvMessagesScreen::handleLongPress() {
     if (!_lxmf) return false;
+    // Only consume long-press once the user has actively navigated into
+    // the list. Otherwise let main.cpp blank the screen.
+    if (!_focusActive) return false;
     int idx = getFocusedPeerIdx();
     if (idx < 0 || idx >= (int)_sortedPeers.size()) return false;
     _lpPeerIdx = idx;

src/ui/screens/LvNodesScreen.cpp

@@ -324,6 +324,9 @@ void LvNodesScreen::updateNicknameDisplay() {
 
 bool LvNodesScreen::handleLongPress() {
     if (!_am) return false;
+    // Only consume long-press once the user has actively navigated into
+    // the list. Otherwise let main.cpp blank the screen.
+    if (!_focusActive) return false;
     int nodeIdx = getFocusedNodeIdx();
     if (nodeIdx < 0 || nodeIdx >= (int)_am->nodes().size()) return false;
     const auto& node = _am->nodes()[nodeIdx];