🔧 Improve file transfer system integration and message handling

- File Transfer Integration: Refactored file transfer system initialization with better error handling and automatic retry mechanisms
- Message Filtering: Added comprehensive message filtering system to prevent file transfer and system messages from appearing in chat UI
- Callback System: Simplified file transfer callback system - removed progress notifications from chat to reduce noise
- System Message Deduplication: Implemented notification flags to prevent duplicate system messages (verification, security upgrades, etc.)
- Error Handling: Enhanced error handling with graceful fallbacks instead of throwing exceptions that could break connections
- UI Message Delivery: Added `deliverMessageToUI()` method with built-in filtering for system/file messages
- DataChannel Event Handling: Improved onmessage handler with early filtering for file transfer messages
- Global Integration: Better integration with global file transfer system (`window.fileTransferSystem`)
- Connection Stability: Removed aggressive reconnection attempts that could cause session closure
- Debug Logging: Enhanced debug logging for better troubleshooting

- File transfer messages now bypass chat UI entirely
- System messages are deduplicated using internal flags
- Better separation of concerns between WebRTC and file transfer systems
- More robust initialization sequence with proper cleanup
- Improved message routing and processing pipeline

- Fixed duplicate system notifications
- Resolved file transfer message leakage into chat
- Improved connection state management
- Better handling of initialization race conditions

index.html

@@ -2963,6 +2963,34 @@
                 }
 
                 const handleMessage = (message, type) => {
+                    // Дополнительная проверка на файловые и системные сообщения
+                    if (typeof message === 'string' && message.trim().startsWith('{')) {
+                        try {
+                            const parsedMessage = JSON.parse(message);
+                            const blockedTypes = [
+                                'file_transfer_start',
+                                'file_transfer_response',
+                                'file_chunk',
+                                'chunk_confirmation',
+                                'file_transfer_complete',
+                                'file_transfer_error',
+                                'heartbeat',
+                                'verification',
+                                'verification_response',
+                                'peer_disconnect',
+                                'key_rotation_signal',
+                                'key_rotation_ready',
+                                'security_upgrade'
+                            ];
+                            if (parsedMessage.type && blockedTypes.includes(parsedMessage.type)) {
+                                console.log(`🛑 Blocked system/file message from chat: ${parsedMessage.type}`);
+                                return; // Не показываем системные и файловые сообщения в чате
+                            }
+                        } catch (parseError) {
+                            // Не JSON - это нормально для обычных текстовых сообщений
+                        }
+                    }
+                    
                     addMessageWithAutoScroll(message, type);
                 };