fix: resolve all 23 MAINTENANCE audit tickets

- deps guards before -h|--help in docker-health/ps, network-scan,
  usb-server, media-mp3/mp4 (--dry-run pre-scan kept); system-firewall
  gains usage()/--help; autostart/usb-automount get flags.sh + template
- install.sh: normalize N-M range syntax in --steps
- bin/pos: INTERACTIVE_CMDS += docker-compose docker-vbox network-hotspot
- common.sh: canonical XDG-aware CONFIG_DIR + DIM color var; notify.sh
  stderr fallback; ent_plugin_* registry renames (runtime plugin API kept)
- docker-compose SCALE_DIR/CONFIG_ENV env seams; ffmpeg in PACKAGES;
  scrcpy.sh exec bit
- docs: health is console-only (--send/--markdown removed), POS.md file
  refs for config/tree/entertainment, DEV.md no-guard exception, docmap/
  filetable regenerated (make gen), hand-maintained line rows bumped
- add scripts/lint-conventions.sh gate + Makefile lint target; record
  all VERIFIED outcomes in MAINTENANCE.md; AGENT_TODO Done entry
  (2026-08-14)
- gates: make gen/check/lint all green (0 FAIL, 0 WARN); bash -n sweep
  clean; restricted-PATH dep tests + step-matrix dry-runs verified

bin/pos

@@ -256,7 +256,7 @@ MAIN_LOG="$LOG_DIR/pos.log"
 log_cmd() { echo "[$(date '+%Y-%m-%d %H:%M:%S')] $* → exit $2" >> "$MAIN_LOG"; }
 
 # Commands that read from stdin interactively — only log invocation
-INTERACTIVE_CMDS="system-firewall media-mp4 system-backup share-usb-server share-smb-server share-smb-client communication-telegram-listener communication-matrix-listener ai-gemini system-schedule entertainment-config config"
+INTERACTIVE_CMDS="docker-compose docker-vbox network-hotspot system-firewall media-mp4 system-backup share-usb-server share-smb-server share-smb-client communication-telegram-listener communication-matrix-listener ai-gemini system-schedule entertainment-config config"
 
 for ((i=n-1; i>=0; i--)); do
     cmd="pos"