test(live): align mqtt/postgres/mysql live tests with honeypot + loop realities

Three unrelated test-correctness fixes exposed by running tests/live:

- test_mqtt_live: honeypot defaults to auth-required (post-2018
  realistic broker). Anonymous CONNECT is rejected with CONNACK rc=5,
  which the "accept" / "subscribe" tests misread as a failure. Pass
  MQTT_ACCEPT_ALL=1 via a new env= override on the live_service factory
  so only those two tests opt into accept-all.
- test_postgres_live::test_auth_hash_logged: connected with
  dbname='prod', which isn't in the honeypot's per-instance DB list, so
  Postgres (correctly) rejected at startup before asking for a
  password — blowing past the auth event the test asserts on. Target
  'postgres' (always in _BASE_DBS) to reach the auth stage.
- test_mysql_backend_live: the module-scoped mysql_test_db_url fixture
  is bound to the module loop, but function-scoped tests default to
  their own per-function loops. Any reuse of the asyncmy pool then
  tripped "Future attached to a different loop". Pin the whole module
  with pytest.mark.asyncio(loop_scope='module').

tests/live/conftest.py

@@ -97,7 +97,7 @@ def assert_rfc5424(
 class _ServiceProcess:
     """Manages a live service subprocess and its stdout log queue."""
 
-    def __init__(self, service: str, port: int):
+    def __init__(self, service: str, port: int, extra_env: dict | None = None):
         template_dir = _TEMPLATES / service
         env = {
             **os.environ,
@@ -106,6 +106,8 @@ class _ServiceProcess:
             "PYTHONPATH": str(template_dir),
             "LOG_TARGET": "",
         }
+        if extra_env:
+            env.update(extra_env)
         self._proc = subprocess.Popen(
             [_PYTHON, str(template_dir / "server.py")],
             cwd=str(template_dir),
@@ -150,9 +152,9 @@ def live_service() -> Generator:
     """
     started: list[_ServiceProcess] = []
 
-    def _start(service: str) -> tuple[int, callable]:
+    def _start(service: str, env: dict | None = None) -> tuple[int, callable]:
         port = _free_port()
-        svc = _ServiceProcess(service, port)
+        svc = _ServiceProcess(service, port, extra_env=env)
         started.append(svc)
         if not _wait_for_port(port):
             svc.stop()

tests/live/test_mqtt_live.py

@@ -9,7 +9,11 @@ from tests.live.conftest import assert_rfc5424
 @pytest.mark.live
 class TestMQTTLive:
     def test_connect_accepted(self, live_service):
-        port, drain = live_service("mqtt")
+        # The honeypot defaults to auth-required (post-2018 realistic
+        # broker posture). Opt into accept-all mode to exercise the
+        # happy-path CONNACK rc=0 code path. See decnet/templates/mqtt/
+        # server.py::MQTT_ACCEPT_ALL.
+        port, drain = live_service("mqtt", env={"MQTT_ACCEPT_ALL": "1"})
         connected = []
         client = mqtt.Client(client_id="test-scanner")
         client.on_connect = lambda c, u, f, rc: connected.append(rc)
@@ -48,7 +52,9 @@ class TestMQTTLive:
         )
 
     def test_subscribe_logged(self, live_service):
-        port, drain = live_service("mqtt")
+        # SUBSCRIBE is gated on successful auth — accept-all lets the test
+        # reach the subscribe path without planting credentials.
+        port, drain = live_service("mqtt", env={"MQTT_ACCEPT_ALL": "1"})
         subscribed = []
         client = mqtt.Client(client_id="sub-test")
         client.on_subscribe = lambda c, u, mid, qos: subscribed.append(mid)

tests/live/test_mysql_backend_live.py

@@ -38,6 +38,13 @@ LIVE_URL = "mysql+asyncmy://root:root@127.0.0.1:3307/decnet"
 
 pytestmark = [
     pytest.mark.live,
+    # Pin every test in this module to the module-scoped event loop. The
+    # module-scoped ``mysql_test_db_url`` fixture (and transitively the
+    # asyncmy connection pool it seeds) is bound to that loop; running the
+    # tests on their own per-function loops trips pytest-asyncio's
+    # "Future attached to a different loop" guard the instant the repo
+    # reuses a pooled connection.
+    pytest.mark.asyncio(loop_scope="module"),
     pytest.mark.skipif(
         not (LIVE_URL and LIVE_URL.startswith("mysql")),
         reason="Set DECNET_DB_URL=mysql+aiomysql://... to run MySQL live tests",

tests/live/test_postgres_live.py

@@ -60,13 +60,18 @@ class TestPostgresLive:
     def test_auth_hash_logged(self, live_service):
         port, drain = live_service("postgres")
         import psycopg2
+        # Real PG rejects before asking for a password when the requested
+        # db doesn't exist, and the honeypot faithfully mirrors that. So
+        # we must target an always-present database (``postgres`` is in
+        # _BASE_DBS) to get past startup and into the password-auth stage
+        # that this test is asserting on.
         try:
             psycopg2.connect(
                 host="127.0.0.1",
                 port=port,
                 user="root",
                 password="toor",
-                dbname="prod",
+                dbname="postgres",
                 connect_timeout=5,
             )
         except psycopg2.OperationalError: