qbittorrent: it listens on the port the mesh gave it, rather than fixing it

The manifest published 8112:8112 and 6881:6881 because qBittorrent refuses
a Host naming another port and announces its torrent port to peers — so the
machine port must equal the software's. Fixing the number in the manifest
states a machine port in a definition. Instead the server runs on the host
network and listens where the mesh put it (WEBUI_PORT=${port:8112},
TORRENTING_PORT=${port:6881}): the two are equal by construction on every
machine, and an assignment still pins 8112/6881 where clients know them.

Verified: the pinned image on the host network with WEBUI_PORT=18710 and
TORRENTING_PORT=18711 served the web UI on 18710 (200, no Host mismatch)
and listened for peers on 18711 tcp+udp.

modules/qbittorrent/module.json

@@ -20,21 +20,21 @@
       "port": 8112,
       "protocol": "tcp",
       "from": "mesh",
-      "why": "the download client's pages, and the WebUI API its consumers and its own tools call; qBittorrent refuses a request whose Host names a port other than the one it listens on, so a caller dialling the machine port gets in only when the machine publishes the same number"
+      "why": "the download client's pages, and the WebUI API its consumers and its own tools call. qBittorrent refuses a request whose Host names a port other than the one it listens on, so it listens on the machine port itself (host network, WEBUI_PORT=${port:8112}) and the two cannot differ on any machine"
     },
     {
       "name": "peers",
       "port": 6881,
       "protocol": "tcp",
       "from": "mesh",
-      "why": "incoming BitTorrent peer connections; the client announces this number to trackers and peers, so the machine must publish it on the same one"
+      "why": "incoming BitTorrent peer connections; announced to trackers and peers, so qBittorrent listens on the machine port itself (TORRENTING_PORT=${port:6881})"
     },
     {
       "name": "peers-udp",
       "port": 6881,
       "protocol": "udp",
       "from": "mesh",
-      "why": "DHT and uTP on the same number as the peer port; announced like it, so published on the same one"
+      "why": "DHT and uTP on the same number as the peer port"
     }
   ],
   "accesses": [
@@ -71,17 +71,14 @@
         "PUID": "1000",
         "PGID": "1000",
         "TZ": "Etc/UTC",
-        "WEBUI_PORT": "8112"
+        "WEBUI_PORT": "${port:8112}",
+        "TORRENTING_PORT": "${port:6881}"
       },
-      "ports": [
-        "8112:8112",
-        "6881:6881",
-        "6881:6881/udp"
-      ],
       "volumes": [
         "${dir:config}:/config",
         "/services/media/downloads:/downloads"
-      ]
+      ],
+      "network": "host"
     },
     {
       "id": "runtime-config",