feat: background download service + queue persistence (v1.6.1)

- Add foreground service for background downloads with wake lock
- Persist download queue to SharedPreferences for app restart recovery
- Fix share intent causing app restart (singleTask + onNewIntent)
- Fix back button clearing state during loading
- Upgrade Kotlin to 2.3.0 for share_plus 12.0.1 compatibility
- Add WAKE_LOCK permission for foreground service

lib/providers/download_queue_provider.dart

@@ -348,6 +348,17 @@ class DownloadQueueNotifier extends Notifier<DownloadQueueState> {
               progress: bytesReceived,
               total: bytesTotal,
             );
+            
+            // Update foreground service notification (Android)
+            if (Platform.isAndroid) {
+              PlatformBridge.updateDownloadServiceProgress(
+                trackName: currentItem.track.name,
+                artistName: currentItem.track.artistName,
+                progress: bytesReceived,
+                total: bytesTotal,
+                queueCount: state.queuedCount,
+              ).catchError((_) {}); // Ignore errors
+            }
           }
           
           // Log progress
@@ -403,6 +414,17 @@ class DownloadQueueNotifier extends Notifier<DownloadQueueState> {
               progress: bytesReceived,
               total: bytesTotal > 0 ? bytesTotal : 1,
             );
+            
+            // Update foreground service notification (Android)
+            if (Platform.isAndroid) {
+              PlatformBridge.updateDownloadServiceProgress(
+                trackName: downloadingItems.first.track.name,
+                artistName: downloadingItems.first.track.artistName,
+                progress: bytesReceived,
+                total: bytesTotal > 0 ? bytesTotal : 1,
+                queueCount: state.queuedCount,
+              ).catchError((_) {}); // Ignore errors
+            }
           }
         }
       } catch (e) {
@@ -742,6 +764,24 @@ class DownloadQueueNotifier extends Notifier<DownloadQueueState> {
     // Track total items at start for notification
     _totalQueuedAtStart = state.items.where((i) => i.status == DownloadStatus.queued).length;
 
+    // Start foreground service to keep downloads running in background (Android only)
+    if (Platform.isAndroid && _totalQueuedAtStart > 0) {
+      final firstItem = state.items.firstWhere(
+        (item) => item.status == DownloadStatus.queued,
+        orElse: () => state.items.first,
+      );
+      try {
+        await PlatformBridge.startDownloadService(
+          trackName: firstItem.track.name,
+          artistName: firstItem.track.artistName,
+          queueCount: _totalQueuedAtStart,
+        );
+        _log.d('Foreground service started');
+      } catch (e) {
+        _log.e('Failed to start foreground service: $e');
+      }
+    }
+
     // Ensure output directory is initialized before processing
     if (state.outputDir.isEmpty) {
       _log.d('Output dir empty, initializing...');
@@ -771,6 +811,16 @@ class DownloadQueueNotifier extends Notifier<DownloadQueueState> {
 
     _stopProgressPolling();
     
+    // Stop foreground service (Android only)
+    if (Platform.isAndroid) {
+      try {
+        await PlatformBridge.stopDownloadService();
+        _log.d('Foreground service stopped');
+      } catch (e) {
+        _log.e('Failed to stop foreground service: $e');
+      }
+    }
+    
     // Final cleanup after queue finishes
     if (_downloadCount > 0) {
       _log.d('Final connection cleanup...');

lib/screens/main_shell.dart

@@ -150,8 +150,9 @@ class _MainShellState extends ConsumerState<MainShell> {
           return;
         }
         
-        // If on Search tab and has text in search bar or has content, clear it
-        if (_currentIndex == 0 && (trackState.hasSearchText || trackState.hasContent || trackState.isLoading)) {
+        // If on Search tab and has text in search bar or has content (but not loading), clear it
+        // Don't clear while loading - this prevents clearing during share intent processing
+        if (_currentIndex == 0 && !trackState.isLoading && (trackState.hasSearchText || trackState.hasContent)) {
           ref.read(trackProvider.notifier).clear();
           return;
         }
@@ -162,6 +163,11 @@ class _MainShellState extends ConsumerState<MainShell> {
           return;
         }
         
+        // If loading, ignore back press
+        if (trackState.isLoading) {
+          return;
+        }
+        
         // Already at root, show exit dialog
         final shouldPop = await _showExitDialog();
         if (shouldPop && context.mounted) {

lib/screens/track_metadata_screen.dart

@@ -938,9 +938,11 @@ class _TrackMetadataScreenState extends ConsumerState<TrackMetadataScreen> {
       return;
     }
     
-    await Share.shareXFiles(
-      [XFile(item.filePath)],
-      text: '${item.trackName} - ${item.artistName}',
+    await SharePlus.instance.share(
+      ShareParams(
+        files: [XFile(item.filePath)],
+        text: '${item.trackName} - ${item.artistName}',
+      ),
     );
   }
 

lib/services/platform_bridge.dart

@@ -234,4 +234,45 @@ class PlatformBridge {
   static Future<void> cleanupConnections() async {
     await _channel.invokeMethod('cleanupConnections');
   }
+
+  /// Start foreground download service to keep downloads running in background
+  static Future<void> startDownloadService({
+    String trackName = '',
+    String artistName = '',
+    int queueCount = 0,
+  }) async {
+    await _channel.invokeMethod('startDownloadService', {
+      'track_name': trackName,
+      'artist_name': artistName,
+      'queue_count': queueCount,
+    });
+  }
+
+  /// Stop foreground download service
+  static Future<void> stopDownloadService() async {
+    await _channel.invokeMethod('stopDownloadService');
+  }
+
+  /// Update download service notification progress
+  static Future<void> updateDownloadServiceProgress({
+    required String trackName,
+    required String artistName,
+    required int progress,
+    required int total,
+    required int queueCount,
+  }) async {
+    await _channel.invokeMethod('updateDownloadServiceProgress', {
+      'track_name': trackName,
+      'artist_name': artistName,
+      'progress': progress,
+      'total': total,
+      'queue_count': queueCount,
+    });
+  }
+
+  /// Check if download service is running
+  static Future<bool> isDownloadServiceRunning() async {
+    final result = await _channel.invokeMethod('isDownloadServiceRunning');
+    return result as bool;
+  }
 }