fix(dispatcharr): forward nginx port for M3U URLs on new installs

Dispatcharr builds absolute proxy URLs from reverse-proxy headers. Without X-Forwarded-Port, downloaded M3U playlists omit :9191.

Fixes #14839

Co-authored-by: Cursor <cursoragent@cursor.com>

install/dispatcharr-install.sh

@@ -121,6 +121,7 @@ server {
     # All other requests proxy to uWSGI
     location / {
         include proxy_params;
+        proxy_set_header X-Forwarded-Port \$server_port;
         proxy_pass http://127.0.0.1:5656;
     }
 }