fix: increase RAG service proxy timeout to 600s

- Increase proxy_read_timeout from 300s to 600s for large PDF uploads
- Add proxy_send_timeout 600s (was defaulting to 60s)
- Fixes 504 Gateway Timeout when uploading 7.5MB+ IFRS PDFs

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

nginx/conf.d/default.conf

@@ -564,7 +564,8 @@ server {
         proxy_set_header X-Real-IP $remote_addr;
         proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
         proxy_set_header X-Forwarded-Proto https;
-        proxy_read_timeout 300s;
+        proxy_read_timeout 600s;
+        proxy_send_timeout 600s;
     }
 }