design: implement dynamic theme-based app icons for system tray and taskbar

frontend/src/theme/ThemeContext.tsx

@@ -31,8 +31,18 @@ export const AppThemeProvider: React.FC<{ children: React.ReactNode }> = ({ chil
     if (api?.updateServerConfig) {
       await api.updateServerConfig({ theme });
     }
+    if (api?.updateAppIcon) {
+      await api.updateAppIcon(theme);
+    }
   };
 
+  useEffect(() => {
+    const api = (window as any).electronAPI;
+    if (api?.updateAppIcon && currentTheme) {
+      api.updateAppIcon(currentTheme);
+    }
+  }, [currentTheme]);
+
   const theme = useMemo(() => getTheme(currentTheme), [currentTheme]);
 
   return (