bdfc0bf060
- Add concurrent download support via Kotlin coroutines - Refactor downloadRemoteNotes() to use async/awaitAll pattern - Implement configurable parallelism level (default: 3 concurrent downloads) - Update progress callback for parallel operations tracking - Add individual download timeout handling - Graceful sequential fallback on concurrent errors - Optimize network utilization for faster sync operations - Preserve conflict detection and state management during parallel downloads Closes #IMPL_005