fix: play button red flash on app start

Use optimistic rendering for file existence check - assume file exists while async check runs, only show error if file is actually missing

CHANGELOG.md

@@ -10,6 +10,9 @@
 - **Branding**: Changed idle screen title from "Search Music" to "SpotiFLAC"
 - **About Page Redesign**: New Material Expressive 3 grouped layout with app header, contributors section with GitHub avatars, and organized links
 
+### Fixed
+- **Play Button Flash**: Fixed play button briefly showing red error icon on app start (now uses optimistic rendering)
+
 ### Performance
 - **Optimized State Management**: Use `.select()` for Riverpod providers to prevent unnecessary widget rebuilds
 - **List Keys**: Added keys to all list builders for efficient list updates and reordering

lib/screens/queue_tab.dart

@@ -16,27 +16,41 @@ class QueueTab extends ConsumerStatefulWidget {
 
 class _QueueTabState extends ConsumerState<QueueTab> {
   final Map<String, bool> _fileExistsCache = {};
+  final Set<String> _pendingChecks = {}; // Track pending async checks
   static const int _maxCacheSize = 500; // Limit cache size to prevent memory leak
 
+  /// Check if file exists - returns true optimistically while checking
+  /// This prevents the "red flash" on app start
   bool _checkFileExists(String? filePath) {
     if (filePath == null) return false;
+    
+    // If already cached, return cached value
     if (_fileExistsCache.containsKey(filePath)) {
       return _fileExistsCache[filePath]!;
     }
     
+    // If check is pending, return true optimistically (assume file exists)
+    if (_pendingChecks.contains(filePath)) {
+      return true;
+    }
+    
     // Limit cache size - remove oldest entry if full
     if (_fileExistsCache.length >= _maxCacheSize) {
       _fileExistsCache.remove(_fileExistsCache.keys.first);
     }
     
+    // Mark as pending and start async check
+    _pendingChecks.add(filePath);
     Future.microtask(() async {
       final exists = await File(filePath).exists();
+      _pendingChecks.remove(filePath);
       if (mounted && _fileExistsCache[filePath] != exists) {
         setState(() => _fileExistsCache[filePath] = exists);
       }
     });
-    _fileExistsCache[filePath] = false;
-    return false;
+    
+    // Return true optimistically while checking
+    return true;
   }
 
   Future<void> _openFile(String filePath) async {