chore: remove /dev/diagram test page

No longer needed — the ProcessDiagram is now integrated into
ExchangeDetail via the ExecutionDiagram wrapper.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/router.tsx

@@ -20,7 +20,6 @@ const DatabaseAdminPage = lazy(() => import('./pages/Admin/DatabaseAdminPage'));
 const OpenSearchAdminPage = lazy(() => import('./pages/Admin/OpenSearchAdminPage'));
 const AppConfigPage = lazy(() => import('./pages/Admin/AppConfigPage'));
 const SwaggerPage = lazy(() => import('./pages/Swagger/SwaggerPage'));
-const DevDiagram = lazy(() => import('./pages/DevDiagram/DevDiagram'));
 
 function SuspenseWrapper({ children }: { children: React.ReactNode }) {
   return (
@@ -64,7 +63,6 @@ export const router = createBrowserRouter([
             ],
           },
           { path: 'api-docs', element: <SuspenseWrapper><SwaggerPage /></SuspenseWrapper> },
-          { path: 'dev/diagram', element: <SuspenseWrapper><DevDiagram /></SuspenseWrapper> },
         ],
       },
     ],