fix(dankserver): arr stack runs with userns_mode host — stack never booted rootless

The arr services were committed (b9de886) with PUID=0 but no userns_mode.
Under rootless podman's default subuid mapping, container-root cannot write
host-root-owned bind mounts, so every app died in logger init
(UnauthorizedAccessException on /config/Sentry) before binding its port —
the stack 502'd since it was first brought up (2026-09-04 00:33).

Per the fleet convention (AGENTS.md, plex/tautulli migration): PUID=0 +
UserNS=host maps container-root to dank (1000), which owns /opt data roots
and /mnt/entropy. Config dirs chowned 1000:1000 at bring-up.

Also drops a duplicate 'networks: [appnet]' key on prowlarr.

dankserver/compose.yaml

@@ -153,6 +153,7 @@ services:
     image: lscr.io/linuxserver/prowlarr:latest
     container_name: prowlarr
     restart: unless-stopped
+    userns_mode: host
     environment:
       - PUID=0
       - PGID=0
@@ -164,12 +165,12 @@ services:
     networks: [appnet]
     ports:
       - "9696:9696"
-    networks: [appnet]
 
   qbittorrent:
     image: lscr.io/linuxserver/qbittorrent:latest
     container_name: qbittorrent
     restart: unless-stopped
+    userns_mode: host
     environment:
       - PUID=0
       - PGID=0
@@ -187,6 +188,7 @@ services:
     image: lscr.io/linuxserver/radarr:latest
     container_name: radarr
     restart: unless-stopped
+    userns_mode: host
     environment:
       - PUID=0
       - PGID=0
@@ -204,6 +206,7 @@ services:
     image: lscr.io/linuxserver/sonarr:latest
     container_name: sonarr
     restart: unless-stopped
+    userns_mode: host
     environment:
       - PUID=0
       - PGID=0
@@ -221,6 +224,7 @@ services:
     image: lscr.io/linuxserver/lidarr:latest
     container_name: lidarr
     restart: unless-stopped
+    userns_mode: host
     environment:
       - PUID=0
       - PGID=0
@@ -238,6 +242,7 @@ services:
     image: lscr.io/linuxserver/readarr:amd64-1.0.980
     container_name: readarr
     restart: unless-stopped
+    userns_mode: host
     environment:
       - PUID=0
       - PGID=0