feat(smtp_relay): move probe forwarding to realism worker via bus

Attacker probe emails are now forwarded by the master (realism worker)
rather than inside the MACVLAN container, which has no internet gateway.

- New smtp.probe.pending bus topic: ingester publishes when smtp_relay
  message_stored fires; worker subscribes and does the actual delivery
- decnet/orchestrator/drivers/smtp_relay.py: pure-sync forward_probe()
  reads the .eml from disk and sends via smtplib on a thread executor
- worker.py: _run_smtp_probe_listener + _handle_probe_pending subtask;
  limit enforced via count_probe_relays() (DB-backed, restart-safe)
- bounties.py: count_probe_relays() query on probe_relay bounty type
- fleet.py: get_fleet_decky_by_name() to pull service config from DB
- services/smtp_relay.py: upstream_* and probe_limit fields defined in
  config_schema but NOT injected into container env (credentials stay
  out of docker env vars)
- ingester.py: stripped of smtplib; publishes probe.pending and exits
- tests: assert upstream keys absent from container environment

decnet/orchestrator/drivers/smtp_relay.py

@@ -0,0 +1,58 @@
+"""SMTP probe-relay driver.
+
+Forwards the attacker's first probe email via the master's real internet
+connection. The smtp_relay decky runs on MACVLAN and has no gateway access;
+the master (where this worker runs) does.
+
+Called by the realism worker's smtp probe listener, not the main tick loop.
+"""
+from __future__ import annotations
+
+import smtplib
+from pathlib import Path
+from typing import Any
+
+_ARTIFACTS_ROOT_DEFAULT = "/var/lib/decnet/artifacts"
+
+
+def forward_probe(
+    *,
+    svc_cfg: dict[str, Any],
+    stored_as: str,
+    decky_name: str,
+    mail_from: str,
+    rcpt_to: list[str],
+    artifacts_root: str = _ARTIFACTS_ROOT_DEFAULT,
+) -> tuple[bool, str]:
+    """Read the .eml from disk and forward it via the upstream relay.
+
+    Returns (True, "") on success or (False, reason) on failure.
+    Always safe to call in a thread — uses only blocking I/O.
+    """
+    upstream_host = (svc_cfg.get("upstream_host") or "").strip()
+    if not upstream_host:
+        return False, "upstream_host not configured"
+
+    eml_path = Path(artifacts_root) / decky_name / "smtp" / stored_as
+    try:
+        body = eml_path.read_bytes()
+    except OSError as exc:
+        return False, f"cannot read eml: {exc}"
+
+    if not rcpt_to:
+        return False, "no recipients"
+
+    upstream_port  = int(svc_cfg.get("upstream_port") or 25)
+    upstream_user  = (svc_cfg.get("upstream_user") or "").strip()
+    upstream_pass  = (svc_cfg.get("upstream_pass") or "").strip()
+    envelope_from  = (svc_cfg.get("upstream_sender") or "").strip() or mail_from
+
+    try:
+        with smtplib.SMTP(upstream_host, upstream_port, timeout=15) as conn:
+            conn.ehlo()
+            if upstream_user and upstream_pass:
+                conn.login(upstream_user, upstream_pass)
+            conn.sendmail(envelope_from, rcpt_to, body)
+        return True, ""
+    except Exception as exc:
+        return False, str(exc)[:256]