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/tests/test_translations.py

@@ -17,7 +17,8 @@ PY_CALL = re.compile(r"""(?<![\w.])(?:_|gettext|gettext_lazy)\(\s*(?:"([^"]+)"|'
 
 def msgids_in_code() -> set[str]:
     found = set()
-    for template in (PORTAL / "templates").rglob("*.html"):
+    templates = [*(PORTAL / "templates").rglob("*.html"), *(PORTAL / "templates").rglob("*.txt")]
+    for template in templates:
         text = template.read_text(encoding="utf-8")
         found.update(a or b for a, b in TRANS_TAG.findall(text))
         found.update(VARIABLE.sub(r"%(\1)s", body).strip() for body in BLOCKTRANS.findall(text))