feat: Implement UI enhancements and fix burst bug

src/screens/PreviewScreen.tsx

@@ -6,6 +6,7 @@ import {
   Image,
   TouchableOpacity,
   ActivityIndicator,
+  BackHandler,
 } from 'react-native';
 import ViewShot from 'react-native-view-shot';
 import { LinearGradient } from 'expo-linear-gradient';
@@ -96,6 +97,18 @@ export default function PreviewScreen({
   // Idle Timer state
   const idleTimerRef = useRef<any>(null);
 
+  // Hardware Back Press
+  useEffect(() => {
+    const onBackPress = () => {
+      onReset();
+      return true; // Prevent default behavior (closing the app)
+    };
+    BackHandler.addEventListener('hardwareBackPress', onBackPress);
+    return () => {
+      BackHandler.removeEventListener('hardwareBackPress', onBackPress);
+    };
+  }, [onReset]);
+
   // Frame state
   const [selectedFrameId, setSelectedFrameId] = useState<string | null>(
     frameMode === 'always' ? initialFrameId : null
@@ -106,7 +119,7 @@ export default function PreviewScreen({
   const currentPhoto = photoUris[photoUris.length - 1];
 
   // Get the active frame asset
-  const activeFrame = selectedFrameId && photoUris.length === 1
+  const activeFrame = selectedFrameId 
     ? FRAMES.find((f) => f.id === selectedFrameId)
     : null;
 
@@ -578,7 +591,7 @@ export default function PreviewScreen({
             </Text>
           </TouchableOpacity>
 
-          {frameMode === 'available' && photoUris.length === 1 && (
+          {frameMode === 'available' && (
             <TouchableOpacity
               style={[styles.editToolBtn, selectedFrameId !== null && styles.editToolBtnActive]}
               onPress={() => {
@@ -603,8 +616,8 @@ export default function PreviewScreen({
           )}
         </View>
 
-        {/* Frame Picker (when mode = available and only 1 photo) */}
-        {frameMode === 'available' && photoUris.length === 1 && (
+        {/* Frame Picker (when mode = available) */}
+        {frameMode === 'available' && (
           <FramePicker
             selectedFrameId={selectedFrameId}
             onSelectFrame={(id) => {