fix: increase Nginx header buffer size for IAP JWT tokens

Increases client_header_buffer_size to 4k and large_client_header_buffers
to 4 16k to handle large Google Cloud IAP JWT headers that were causing
500 errors.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

nginx.conf

@@ -2,6 +2,10 @@ server {
     listen 80;
     server_name _;
 
+    # Increase buffer size to handle large IAP JWT headers
+    client_header_buffer_size 4k;
+    large_client_header_buffers 4 16k;
+
     root /usr/share/nginx/html;
     index index.html;