feat: SMTP email notification channel with UI and ingest

Migration 006, email config DB/env, smtplib sender, settings API,
Settings UI section, and dispatch on event/problem ingest.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/tests/test_settings_api.py

@@ -24,6 +24,65 @@ def test_get_notification_settings_masks_secrets(jwt_headers, client, monkeypatc
     assert body["telegram"]["bot_token_hint"].endswith("ghij")
     assert "webhook" in body
     assert body["webhook"]["enabled"] is False
+    assert "email" in body
+    assert body["email"]["enabled"] is False
+
+
+def test_put_email_settings_persists_db(jwt_headers, client, db_session, monkeypatch):
+    monkeypatch.setenv("SMTP_ENABLED", "false")
+    monkeypatch.setenv("SMTP_HOST", "")
+    get_settings.cache_clear()
+
+    response = client.put(
+        "/api/v1/settings/notifications/email",
+        headers=jwt_headers,
+        json={
+            "enabled": True,
+            "min_severity": "warning",
+            "smtp_host": "smtp.example.com",
+            "smtp_port": 587,
+            "smtp_user": "monitor",
+            "smtp_password": "secret",
+            "mail_from": "sac@example.com",
+            "mail_to": "admin@example.com,ops@example.com",
+            "smtp_starttls": True,
+            "smtp_ssl": False,
+        },
+    )
+    assert response.status_code == 200
+    body = response.json()
+    assert body["source"] == "db"
+    assert body["configured"] is True
+    assert body["smtp_port"] == 587
+
+    row = db_session.get(NotificationChannel, "email")
+    assert row is not None
+    assert row.smtp_host == "smtp.example.com"
+    assert row.mail_from == "sac@example.com"
+
+
+def test_post_email_test_success(jwt_headers, client, db_session, monkeypatch):
+    monkeypatch.setenv("SMTP_ENABLED", "false")
+    get_settings.cache_clear()
+
+    db_session.add(
+        NotificationChannel(
+            channel="email",
+            enabled=True,
+            min_severity="warning",
+            smtp_host="smtp.example.com",
+            smtp_port=587,
+            mail_from="sac@example.com",
+            mail_to="admin@example.com",
+        )
+    )
+    db_session.commit()
+
+    with patch("app.api.v1.settings.send_email_test_message") as mock_test:
+        response = client.post("/api/v1/settings/notifications/email/test", headers=jwt_headers)
+    assert response.status_code == 200
+    assert response.json()["ok"] is True
+    mock_test.assert_called_once()
 
 
 def test_put_webhook_settings_persists_db(jwt_headers, client, db_session, monkeypatch):