fix network time precision regression regression

This should really be fixed on the client side too so we can eventually
drop this workaround.

nginx/nginx.conf

@@ -214,6 +214,16 @@ http {
         add_header Strict-Transport-Security "max-age=63072000; includeSubDomains; preload" always;
 
         location = / {
+            # work around regression in port to Android 14 not using /generate_204
+
+            # note: location block keepalive configuration does not work for HTTP/2
+            keepalive_requests 2;
+            keepalive_timeout 15s;
+
+            add_header Strict-Transport-Security "max-age=63072000; includeSubDomains; preload" always;
+            add_header X-Robots-Tag "none" always;
+            add_header X-Time $msec_integer;
+
             return 301 https://grapheneos.org/faq#default-connections;
         }