Abort caption requests when they are not in view to tax the server less.

ui/src/app/api/caption/get/route.ts

@@ -5,8 +5,18 @@ import path from 'path';
 import { getDatasetsRoot } from '@/server/settings';
 
 export async function POST(request: NextRequest) {
-  
-  const body = await request.json();
+  let body;
+  try {
+    body = await request.json();
+  } catch {
+    // Client aborted the request before body was fully sent
+    return new NextResponse(null, { status: 499 });
+  }
+
+  if (request.signal.aborted) {
+    return new NextResponse(null, { status: 499 });
+  }
+
   const { imgPath } = body;
   console.log('Received POST request for caption:', imgPath);
   try {