fix(nginx): don't leak internal port 8443 in directory redirects

nginx listens on 127.0.0.1:8443 behind the stream proxy on port 443.
For a directory requested without a trailing slash, nginx built an
absolute Location header with its own port, e.g.
https://example.org:8443/apps/, which is unreachable from outside.
With absolute_redirect off, nginx sends a relative Location: /apps/.

cmdeploy/src/cmdeploy/nginx/nginx.conf.j2

@@ -68,6 +68,11 @@ http {
   
 		listen 127.0.0.1:8443 ssl default_server;
 
+		# nginx is reached through the stream proxy on port 443,
+		# so redirects it generates itself (e.g. /dir -> /dir/)
+		# must not contain the internal port 8443.
+		absolute_redirect off;
+
 		root {{ www_root }};
 
 		index index.html index.htm;