Bumps the shared default WAN look-back from 15m to 24h (1440m) so
both /phonestatus follow-ups and /voicediag pick up a full day of
voice-quality signal by default — better for after-the-fact ticket
triage than a live snapshot. Operators wanting real-time behavior
can set WAN_STANDARD_WINDOW_MINUTES=15 or pass --window 15m to
/voicediag.
Also fills in a long-standing help gap: /voicediag was fully
implemented but never listed in /help. Adds it under "AV & phones"
with usage, examples, and notes covering detail mode, --only,
--window, thresholds, kill switch, HTTP shape, and audit logging.
Updates /help phonestatus to call out the 24h WAN follow-up +
cross-link to /voicediag.
Co-authored-by: Cursor <cursoragent@cursor.com>