Replaces the unused EMAIL_WEBHOOK_URL stub with a real Microsoft Graph
Mail.Send pipeline via @azure/msal-node client-credentials flow. Prior
state on prod: every alert email was logged to journalctl and never
sent (21 fallback log lines per hour for the chronic-offline devices).
Four coordinated changes shipped as one commit since they're all part
of making email delivery actually work responsibly:
1. services/email.js (NEW): Graph send via plain HTTPS (no SDK), in-memory
MSAL token cache (refresh 60s pre-expiry), graceful stdout fallback
when GRAPH_* env vars absent. Drop-in replacement for the old webhook.
2. services/alerts.js refactored: sequential await around sendEmail (was
parallel fire-and-forget; first run hit Graph's MailboxConcurrency 429
ApplicationThrottled on a 30-device backlog). Sequential at ~250ms per
send takes 5-8s for the full backlog, well within the 60s tick. Also:
24h long-offline cutoff to stop nagging about chronic-offline devices
(the 20,000+ minute ones); 2-hour dedup window (was 1h) via a generic
shouldSendAlert(type, id, windowMs) helper that future alert types
(payment_failed, plan_limit_hit, etc.) can reuse.
3. Preferences UI: single checkbox in settings.js Account section bound
to users.email_alerts. Saved via the existing Save Profile button. PUT
/api/auth/me extended to accept email_alerts. requireAuth middleware
SELECT now includes email_alerts so it propagates via req.user.
4. Dev safety net: GRAPH_DEV_RESTRICT_TO env var as an allow-list. When
set, only listed recipients reach Graph; everyone else is suppressed
with a log line. Prevents local dev (which often runs against fresh
prod DB copies) from accidentally emailing real prod users. UNSET on
prod systemd unit so production fans out normally.
Also: package.json scripts use --env-file-if-exists=.env so local dev
picks up .env automatically (Node 20.6+ built-in, no dotenv dep). Prod
runs via systemd ExecStart and is unaffected. server/.gitignore added
to keep .env out of git.
Smoke verified end-to-end:
- Sequential send pattern verified (a prior parallel-send tick had hit
Graph's MailboxConcurrency 429 on 30 simultaneous sends; sequential
at ~250ms each completes the same backlog without throttling)
- 24h cutoff silenced 20/21 prod devices on the next tick
- Dev restrict suppressed the 1 within-24h send
- User-preference toggle flipped via UI -> DB -> alert path silently
continued before reaching even the suppression log
