fix(chat): add SSE padding to bypass proxy buffering

src/controllers/chat.controller.ts

@@ -33,10 +33,18 @@ function startSse(res: Response) {
   // toplu halde göndermesini önlemek için.
   res.setHeader('X-Accel-Buffering', 'no');
   (res as any).flushHeaders?.();
+  // Cloudflare gibi proxy'lerin buffer'ını aşmak için ~2KB dummy padding gönder.
+  res.write(`: ${' '.repeat(2048)}\n\n`);
+  if (typeof (res as any).flush === 'function') {
+      (res as any).flush();
+  }
 }
 
 function sseWrite(res: Response, payload: Record<string, unknown>) {
   res.write(`data: ${JSON.stringify(payload)}\n\n`);
+  if (typeof (res as any).flush === 'function') {
+      (res as any).flush();
+  }
 }
 
 interface ChatAttachment { filename: string; text: string; }