fix(nginx): do not strip path for Grafana (pass entire /grafana/ prefix)

docker/nginx.conf

@@ -79,7 +79,8 @@ http {
         }
 
         location /grafana/ {
-            proxy_pass http://127.0.0.1:3000/;
+            # Do NOT strip the path. explicit serve_from_sub_path=true in Grafana needs the prefix.
+            proxy_pass http://127.0.0.1:3000;
             proxy_set_header Host $host;
             proxy_set_header X-Real-IP $remote_addr;
             proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;