feat: add centered quick-add item button in bottom nav

src/AppRoot.js

@@ -727,6 +727,14 @@ export default function AppRoot() {
     }, 80);
   }
 
+  function openQuickAddItemFromNav() {
+    if (!selectedTripId) {
+      showAlert('No trip selected', 'Please select or create a trip first.');
+      return;
+    }
+    openAddItemModal();
+  }
+
   if (!loaded) {
     return (
       <SafeAreaView style={[styles.safe, { paddingTop: topInset }]}>
@@ -817,7 +825,7 @@ export default function AppRoot() {
         </ScrollView>
       </KeyboardAvoidingView>
 
-      <BottomTab current={tab} onChange={setTab} />
+      <BottomTab current={tab} onChange={setTab} onAddItem={openQuickAddItemFromNav} canAddItem={!!selectedTripId} />
 
       <DatePickerModal
         visible={datePicker.visible}