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

docker/gunicorn.conf.py

@@ -0,0 +1,7 @@
+"""gunicorn settings that need code. The scheduler runs inside the single worker (AD-12)."""
+
+
+def post_worker_init(worker):
+    from portal.scheduler.runner import runner
+
+    runner.start()