Rework PSTN trunk: role-based permissions, ring-groups, ntfy spend alerts

Generalizes services/pstn-trunk.sh (renamed from voipms-trunk.sh in the
prior commit) away from VoIP.ms specifics - any IP-authenticated SIP
provider works, VoIP.ms is just the suggested default. Adds:

- Role-based outbound permission: a configurable allow-list of extensions
  that may dial PSTN numbers (regex-gated on CHANNEL(peername)), separate
  from internal extension-to-extension dialing which stays open to everyone
  regardless. Blank list preserves the original "everyone can dial out"
  behavior.
- Inbound ring-group: rings a configurable list of extensions instead of a
  single hardcoded one.
- ntfy alerts: immediate on denied (unauthorized extension) or rejected
  (concurrency cap hit) calls, plus an hourly cron-driven check that alerts
  once per month when estimated spend crosses a threshold and every hour
  call volume looks like a burst. Uses a self-contained pipe-delimited call
  log rather than Asterisk's CDR, to avoid depending on CDR module
  availability and CSV comma-quoting.
- Settings persisted to .pstn-trunk.env so "update in place" reapplies
  everything from that file instead of fragile re-parsing out of generated
  Asterisk config (which had a real bug: update mode was extracting the
  wrong Dial(PJSIP/...) line).

Tested end-to-end against a sandboxed copy of the real vendor files:
permission-gate regex, ring-group dial-string construction, ntfy line
injection/removal, and the usage-alert script's threshold/burst/monthly-
dedup logic all verified with synthetic data. Caught and fixed a sed `&`
escaping bug in the ring-group substitution before it shipped (RING_DIAL
contains literal `&` join characters, which sed's replacement syntax
otherwise treats as "insert the match").

setup.sh

@@ -89,7 +89,7 @@ is_installed() {
         sync-cc) [ -f "$ACTUAL_HOME/sync-cc/sync_cc.py" ] ;;
         sky-cam) [ -d "$ACTUAL_HOME/sky-cam/.git" ] ;;
         sky-cam-frigate) [ -d "$ACTUAL_HOME/sky-cam/.git" ] && [ -f "$ACTUAL_HOME/sky-cam/frigate-retime.sh" ] ;;
-        voipms-trunk) [ -f "$DOCKER_DIR/asterisk-digital-ocean/config/asterisk/voipms-trunk-pjsip.conf" ] ;;
+        pstn-trunk) [ -f "$DOCKER_DIR/asterisk-digital-ocean/config/asterisk/pstn-trunk-pjsip.conf" ] ;;
         ssh-config) false ;;   # repeatable management tool, never shows [installed]
         *) [ -e "$DOCKER_DIR/$1" ] ;;
     esac