fix: reconcile desktop latest.json after deploy; nginx MIME types

Run reload-frontend-desktop-static from post-receive after deploy so
signed updater manifest survives git checkout placeholder reset.

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

frontend/nginx.conf

@@ -145,7 +145,11 @@ server {
     location /desktop/updates/ {
         alias /usr/share/nginx/html/desktop/updates/;
         add_header Cache-Control "no-cache, no-store, must-revalidate";
+    }
+    location = /desktop/updates/latest.json {
+        alias /usr/share/nginx/html/desktop/updates/latest.json;
         default_type application/json;
+        add_header Cache-Control "no-cache, no-store, must-revalidate";
     }
 
     # gzip 압축