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/settings/routes.py

@@ -319,7 +319,8 @@ async def test_email():
     the zone chosen for them. A blank password uses the saved one."""
     from steward.core.formatting import zone
     from steward.core.mail import Recipient, alert_email, is_real_address, pick_recipients
-    from steward.core.notifications import _send_email, smtp_mode
+    from steward.core import outbox
+    from steward.core.notifications import smtp_mode
     from steward.models.users import User
     form = await request.form
     async with current_app.db_sessionmaker() as db:
@@ -345,11 +346,12 @@ async def test_email():
             "email", False, "Your account has no email address mail can reach, and no Also send to "
                             "addresses are entered. Set your address on the Account page.")
     alert = _sample_alert()
-    sent = await _send_email(cfg, alert, to)
+    # Queued and recorded like any email, tried once with the form's values.
+    ok, said = outbox.said(await outbox.send_each(
+        current_app, "test", to, lambda r: alert_email(cfg, alert, r), retry=False, cfg=cfg))
     how = {"ssl": "implicit TLS", "starttls": "STARTTLS", "plain": "no TLS"}[smtp_mode(port, cfg["tls"])]
-    result = (f"Sent to {', '.join(r.address for r in to)} via {cfg['host']}:{port} ({how})."
-              if sent["sent"] else f"{cfg['host']}:{port} ({how}): {sent['error']}")
-    return await _notify_test_result("email", sent["sent"], result, alert_email(cfg, alert, to[0])[1])
+    result = f"{said[:-1]} via {cfg['host']}:{port} ({how})." if ok else f"{cfg['host']}:{port} ({how}): {said}"
+    return await _notify_test_result("email", ok, result, alert_email(cfg, alert, to[0])[1])
 
 
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