feat(email): each account gets its own email, in its own zone (milestone 495)

Milestone 495 "Email goes to each account, in its own time zone", on the
operator's ruling (System 156): notifications go to each user, times in
their zone, defaults on, toggled per user or per role.

- users.notify_alerts / notify_report (migration 0036): None follows the
  role's default, notify.<kind>.<role> in settings, all on to start.
- mail.pick_recipients: active accounts that want the email and have an
  address mail can reach (an SSO placeholder like name@oidc is skipped and
  flagged), each in its own zone with no UTC beside it, then the Also send
  to addresses in their chosen zone with UTC beside. One copy per address,
  all over one SMTP connection.
- Alerts, the weekly report and the test email (to you, in your zone, plus
  the typed addresses) send that way. The save-time smtp.tz capture is gone.
- Notifications: a role × email table of defaults, who each email reaches
  and who can't be reached, and Also send to with its own zone, which starts
  as the first admin's to open the page.
- Account page: your address and your two switches. Users: an Emailed
  column, and an admin sets an account's switches on its page.
- The Alerts page counts the accounts it emails. zone_select macro and
  formatting.zones_by_region shared by Account and Notifications.

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

steward/core/notifications.py

@@ -1,5 +1,4 @@
 from __future__ import annotations
-import asyncio
 import json
 import logging
 import smtplib
@@ -17,12 +16,15 @@ async def dispatch_notifications(
     smtp_cfg: dict,
     webhook_cfg: dict,
     alert_data: dict,
+    recipients: list = (),
 ) -> dict:
-    """Dispatch all configured notification channels. Returns results dict."""
+    """Dispatch all configured notification channels: email to each of
+    `recipients` (mail.Recipient, from mail.recipients) when a server is set.
+    Returns results dict."""
     results = {}
 
-    if smtp_cfg.get("host") and smtp_cfg.get("recipients"):
-        results["email"] = await _send_email(smtp_cfg, alert_data)
+    if smtp_cfg.get("host") and recipients:
+        results["email"] = await _send_email(smtp_cfg, alert_data, recipients)
 
     if webhook_cfg.get("url"):
         results["webhook"] = await _send_webhook(webhook_cfg, alert_data)
@@ -41,20 +43,19 @@ def smtp_mode(port, tls) -> str:
     return "starttls" if tls else "plain"
 
 
-async def _send_email(cfg: dict, alert: dict) -> dict:
-    from steward.core.mail import alert_email, message
+async def _send_email(cfg: dict, alert: dict, recipients: list) -> dict:
+    """Each recipient their own copy, in their own zone, over one connection."""
+    from steward.core.mail import alert_email, message, send
     try:
-        subject, text, html = alert_email(cfg, alert)
-        msg = message(cfg, subject, text, html)
-        loop = asyncio.get_running_loop()
-        await loop.run_in_executor(None, _smtp_send_sync, cfg, msg)
+        messages = [message(cfg, to.address, *alert_email(cfg, alert, to)) for to in recipients]
+        await send(cfg, messages)
         return {"sent": True, "error": None}
     except Exception as exc:
         logger.error(f"Email notification failed: {exc}")
         return {"sent": False, "error": str(exc)}
 
 
-def _smtp_send_sync(cfg: dict, msg: EmailMessage) -> None:
+def _smtp_send_sync(cfg: dict, messages: list[EmailMessage]) -> None:
     port = int(cfg.get("port") or 587)
     mode = smtp_mode(port, cfg.get("tls", True))
     ctx = ssl.create_default_context()
@@ -67,7 +68,8 @@ def _smtp_send_sync(cfg: dict, msg: EmailMessage) -> None:
             smtp.starttls(context=ctx)
         if cfg.get("username"):
             smtp.login(cfg["username"], cfg.get("password", ""))
-        smtp.send_message(msg)
+        for msg in messages:
+            smtp.send_message(msg)
 
 
 def _json_str(value) -> str: