Sidecars dial the port they were given, not the software's

A host-network sidecar reaches its service over the machine's loopback, and
the mesh publishes that service on a machine port it assigns (ADR 0038) —
so dialling the software's port reaches whatever else holds it. On ace,
searxng's sidecar dialled 127.0.0.1:8080 and got unifi's inform port. The
same shape in bazarr, bookshelf, lidarr, nzbget, qbittorrent, radarr and
sonarr; each now asks with ${port:N} (hq 088). Found in review of ace's
module preparation.

modules/radarr/module.json

@@ -75,7 +75,7 @@
       ],
       "env": {
         "MESH_BROKER_FILE": "/run/secrets/broker",
-        "MESH_RADARR_URL": "http://127.0.0.1:7878",
+        "MESH_RADARR_URL": "http://127.0.0.1:${port:7878}",
         "MESH_RADARR_CONFIG_DIR": "/var/lib/radarr/config"
       },
       "artifact": "runtime"