fix: update sidebar channel icon to use Network component and improve ChannelConfigModal styles

src/components/layout/Sidebar.tsx

@@ -1,5 +1,5 @@
 import { useLocation, useNavigate } from 'react-router-dom';
-import { Book, Bot, Clock, Code, Cpu, House, Link2, Puzzle, Settings } from 'lucide-react';
+import { Book, Bot, Clock, Code, Cpu, House, Network, Puzzle, Settings } from 'lucide-react';
 import { useI18n } from '../../i18n';
 import { NAV_ITEMS, normalizeWorkspacePath } from '../../router/routes';
 
@@ -8,7 +8,7 @@ import blueLogo from '../../assets/images/login/blue_logo.png';
 const MENU_MARKS: Record<string, typeof House> = {
   '/home': House,
   '/knowledge': Book,
-  '/channels': Link2,
+  '/channels': Network,
   '/agents': Bot,
   '/models': Cpu,
   '/skills': Puzzle,