M8-R11: make business timezone deterministic

tests/test_deployment.py

@@ -72,6 +72,21 @@ def test_compose_uses_migration_job_before_app() -> None:
     assert dev["services"]["app"]["build"] == "."
 
 
+def test_compose_defaults_business_timezone_and_dev_inherits_it() -> None:
+    """Both production services receive an overridable Amsterdam timezone.
+
+    Compose merges service ``environment`` mappings, and the dev override does
+    not replace either mapping, so the base default applies to base+dev too.
+    """
+    base = _read_yaml("docker-compose.yml")
+    dev = _read_yaml("docker-compose.dev.yml")
+    default_tz = "${TZ:-Europe/Amsterdam}"
+
+    for service_name in ("migration", "app"):
+        assert base["services"][service_name]["environment"]["TZ"] == default_tz
+        assert "TZ" not in dev["services"].get(service_name, {}).get("environment", {})
+
+
 def test_compose_keeps_app_non_root_and_maps_minimal_warmtelink_serial_access() -> None:
     """Base Compose maps the configured device with only pyserial's required access.