feat(email): the report, invites, resets and test sends go through the outbox; only it talks SMTP (#5508)

#5508 "Every other email through the outbox: weekly report, invites,
password resets, and the test buttons" (milestone 501).

- outbox.send_each queues one email per reader (claimed, so the sender
  doesn't take it too) and tries them at once, for a page that answers
  with what happened; outbox.said words the result. attempt takes a cfg
  for a test of the form's unsaved settings and returns the settled rows.
- Weekly report (scheduled and Send now) and invites: queued, tried at
  once; one the server couldn't take yet is retried for an hour. An invite
  that didn't go shows its link with the reason, as before.
- Password reset: queued in the reset link's own transaction; the sender
  delivers it on its next tick.
- Settings -> Notifications test email and a rule's Send test: queued and
  recorded with retry=False, tried once (System 156 ruling).
- Removed mail.send, notifications._send_email and _smtp_send_sync;
  dispatch_notifications is webhook only. A guard asserts only the outbox
  (and smtp_open itself) opens an SMTP connection, with a self-test.

Also fixes run 8941 (#5507's integration test): its Also-send-to
addresses were "@test", which is_real_address rightly drops; they are
example.com now.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

steward/core/reports.py

@@ -11,7 +11,7 @@ from sqlalchemy import and_, case, func, select
 
 from steward.alerts import service as alert_svc
 from steward.core.formatting import zone
-from steward.core.mail import message, recipients, report_email, send
+from steward.core.mail import recipients, report_email
 from steward.core.settings import get_setting
 from steward.models.alerts import AlertEvent
 from steward.models.metrics import PluginMetric
@@ -134,13 +134,13 @@ async def send_report(app) -> tuple[bool, str]:
         logger.exception("Failed to build report data")
         return False, f"Data collection failed: {exc}"
 
-    try:
-        await send(smtp_cfg, [message(smtp_cfg, r.address, *report_email(smtp_cfg, data, r)) for r in to])
-    except Exception as exc:
-        logger.error("Failed to send weekly report: %s", exc)
-        return False, f"Send failed: {exc}"
-    logger.info("Weekly report sent to %d address(es)", len(to))
-    return True, f"Report sent to {', '.join(r.address for r in to)}."
+    from steward.core import outbox
+    # Queued, then tried at once so the button can say what happened; one
+    # the server didn't take yet stays queued and is retried for an hour.
+    ok, said = outbox.said(await outbox.send_each(
+        app, "report", to, lambda r: report_email(smtp_cfg, data, r)))
+    logger.info("Weekly report: %s", said)
+    return ok, said
 
 
 def report_due(now: datetime, day: int, hour: int, tz) -> bool: