feat: add scheduler and mail outbox

SMTP adapter with TLS and a fake, outbox with retries, backoff, rate limit and restart safety, scheduler tick with job-run records started by gunicorn, and a send_test_mail command.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N3t4WL7bd9bdHHNjEsxzqC

portal/adapters/registry.py

@@ -6,9 +6,11 @@ from django.conf import settings
 
 from .directory import Directory, LdapDirectory
 from .idp import Idp, OidcIdp
+from .mail import Mailer, SmtpMailer
 
 _directory: Directory | None = None
 _idp: Idp | None = None
+_mailer: Mailer | None = None
 
 
 def get_directory() -> Directory:
@@ -25,7 +27,16 @@ def get_idp() -> Idp:
     return _idp
 
 
-def install(directory: Directory | None = None, idp: Idp | None = None) -> None:
+def get_mailer() -> Mailer:
+    global _mailer
+    if _mailer is None:
+        _mailer = SmtpMailer(settings.SMTP)
+    return _mailer
+
+
+def install(
+    directory: Directory | None = None, idp: Idp | None = None, mailer: Mailer | None = None
+) -> None:
     """Replace the adapters (tests). Passing None for one leaves it to be built on first use."""
-    global _directory, _idp
-    _directory, _idp = directory, idp
+    global _directory, _idp, _mailer
+    _directory, _idp, _mailer = directory, idp, mailer