feat(tests): add live subprocess integration test suite for services

Spins up each service's server.py in a real subprocess via a free ephemeral
port (PORT env var), connects with real protocol clients, and asserts both
correct protocol behavior and RFC 5424 log output.

- 44 live tests across 10 services: http, ftp, smtp, redis, mqtt,
  mysql, postgres, mongodb, pop3, imap
- Shared conftest.py: _ServiceProcess (bg reader thread + queue),
  free_port, live_service fixture, assert_rfc5424 helper
- PORT env var added to all 10 targeted server.py templates
- New pytest marker `live`; excluded from default addopts run
- requirements-live-tests.txt: flask, twisted + protocol clients

tests/live/test_smtp_live.py

@@ -0,0 +1,39 @@
+import smtplib
+
+import pytest
+
+from tests.live.conftest import assert_rfc5424
+
+
+@pytest.mark.live
+class TestSMTPLive:
+    def test_banner_received(self, live_service):
+        port, drain = live_service("smtp")
+        with smtplib.SMTP("127.0.0.1", port, timeout=5) as s:
+            code, msg = s.ehlo("test.example.com")
+        assert code == 250
+
+    def test_ehlo_logged(self, live_service):
+        port, drain = live_service("smtp")
+        with smtplib.SMTP("127.0.0.1", port, timeout=5) as s:
+            s.ehlo("attacker.example.com")
+        lines = drain()
+        assert_rfc5424(lines, service="smtp", event_type="ehlo")
+
+    def test_auth_attempt_logged(self, live_service):
+        port, drain = live_service("smtp")
+        with smtplib.SMTP("127.0.0.1", port, timeout=5) as s:
+            s.ehlo("attacker.example.com")
+            try:
+                s.login("admin", "password123")
+            except smtplib.SMTPAuthenticationError:
+                pass  # expected — honeypot rejects auth
+        lines = drain()
+        assert_rfc5424(lines, service="smtp", event_type="auth_attempt")
+
+    def test_connect_disconnect_logged(self, live_service):
+        port, drain = live_service("smtp")
+        with smtplib.SMTP("127.0.0.1", port, timeout=5) as s:
+            s.ehlo("scanner.example.com")
+        lines = drain()
+        assert_rfc5424(lines, service="smtp", event_type="connect")