refactor: remove duplicate MCP service log files

Remove redundant log file creation for MCP services since output is
already captured by Docker logs. This simplifies deployment by removing
unnecessary volume mounts and file management.

Changes:
- Remove logs/ directory creation from Dockerfile
- Remove logs/ volume mount from docker-compose.yml
- Update start_mcp_services.py to send output to DEVNULL
- Update documentation to reflect changes (DOCKER.md, docs/DOCKER.md)
- Update .env.example to remove logs/ from volume description

Users can still view MCP service output via 'docker logs' or
'docker-compose logs -f'. Trading session logs in data/agent_data/
remain unchanged.

agent_tools/start_mcp_services.py

@@ -52,10 +52,6 @@ class MCPServiceManager:
             }
         }
 
-        # Create logs directory
-        self.log_dir = Path('logs')
-        self.log_dir.mkdir(exist_ok=True)
-        
         # Set signal handlers
         signal.signal(signal.SIGINT, self.signal_handler)
         signal.signal(signal.SIGTERM, self.signal_handler)
@@ -77,27 +73,23 @@ class MCPServiceManager:
             return False
 
         try:
-            # Start service process
-            log_file = self.log_dir / f"{service_id}.log"
-
             # Set PYTHONPATH to /app so services can import from tools module
             env = os.environ.copy()
             env['PYTHONPATH'] = str(Path.cwd())
 
-            with open(log_file, 'w') as f:
-                process = subprocess.Popen(
-                    [sys.executable, str(script_path)],
-                    stdout=f,
-                    stderr=subprocess.STDOUT,
-                    cwd=Path.cwd(),  # Use current working directory (/app)
-                    env=env  # Pass environment with PYTHONPATH
-                )
-            
+            # Start service process (output goes to Docker logs)
+            process = subprocess.Popen(
+                [sys.executable, str(script_path)],
+                stdout=subprocess.DEVNULL,
+                stderr=subprocess.DEVNULL,
+                cwd=Path.cwd(),  # Use current working directory (/app)
+                env=env  # Pass environment with PYTHONPATH
+            )
+
             self.services[service_id] = {
                 'process': process,
                 'name': service_name,
-                'port': port,
-                'log_file': log_file
+                'port': port
             }
             
             print(f"✅ {service_name} service started (PID: {process.pid}, Port: {port})")
@@ -167,15 +159,14 @@ class MCPServiceManager:
                 print(f"✅ {service['name']} service running normally")
             else:
                 print(f"❌ {service['name']} service failed to start")
-                print(f"   Please check logs: {service['log_file']}")
+                print(f"   Check Docker logs for details: docker logs ai-trader-server")
     
     def print_service_info(self):
         """Print service information"""
         print("\n📋 Service information:")
         for service_id, service in self.services.items():
             print(f"  - {service['name']}: http://localhost:{service['port']} (PID: {service['process'].pid})")
-        
-        print(f"\n📁 Log files location: {self.log_dir.absolute()}")
+
         print("\n🛑 Press Ctrl+C to stop all services")
     
     def keep_alive(self):