feat(zigbee): add MQTT TLS support with optional cert verify skip

- Schema: mqtt_tls + mqtt_tls_insecure flags on import + test-connection
  requests; model_validator enforces insecure requires tls
- Service: _build_tls_context() using ssl.create_default_context();
  logger.warning when verification disabled; tls_context plumbed into
  aiomqtt.Client for both fetch_networkmap and test_mqtt_connection
- Route: passes tls flags through to service
- Frontend: TLS checkbox auto-toggles port 1883<->8883 unless user
  edited; insecure checkbox disabled until TLS on, red-tinted; password
  field marked autocomplete=new-password
- Tests: 7 new backend tests (TLS context build, client kwargs assertion,
  router happy path, insecure-without-tls 422)

backend/tests/test_zigbee_router.py

@@ -152,6 +152,8 @@ async def test_import_with_credentials(client: AsyncClient, headers: dict) -> No
         base_topic="z2m",
         username="admin",
         password="secret",
+        tls=False,
+        tls_insecure=False,
     )
 
 
@@ -226,3 +228,57 @@ async def test_import_missing_mqtt_host(client: AsyncClient, headers: dict) -> N
         headers=headers,
     )
     assert res.status_code == 422
+
+
+@pytest.mark.asyncio
+async def test_import_with_tls_passes_flags(client: AsyncClient, headers: dict) -> None:
+    with patch("app.api.routes.zigbee.fetch_networkmap") as mock_fetch:
+        mock_fetch.return_value = ([], [])
+        res = await client.post(
+            "/api/v1/zigbee/import",
+            json={
+                "mqtt_host": "broker.example.com",
+                "mqtt_port": 8883,
+                "mqtt_tls": True,
+            },
+            headers=headers,
+        )
+    assert res.status_code == 200
+    kwargs = mock_fetch.call_args.kwargs
+    assert kwargs["tls"] is True
+    assert kwargs["tls_insecure"] is False
+
+
+@pytest.mark.asyncio
+async def test_import_tls_insecure_requires_tls(client: AsyncClient, headers: dict) -> None:
+    res = await client.post(
+        "/api/v1/zigbee/import",
+        json={
+            "mqtt_host": "broker.example.com",
+            "mqtt_port": 1883,
+            "mqtt_tls": False,
+            "mqtt_tls_insecure": True,
+        },
+        headers=headers,
+    )
+    assert res.status_code == 422
+
+
+@pytest.mark.asyncio
+async def test_test_connection_with_tls(client: AsyncClient, headers: dict) -> None:
+    with patch("app.api.routes.zigbee.test_mqtt_connection") as mock_conn:
+        mock_conn.return_value = True
+        res = await client.post(
+            "/api/v1/zigbee/test-connection",
+            json={
+                "mqtt_host": "broker.example.com",
+                "mqtt_port": 8883,
+                "mqtt_tls": True,
+                "mqtt_tls_insecure": True,
+            },
+            headers=headers,
+        )
+    assert res.status_code == 200
+    kwargs = mock_conn.call_args.kwargs
+    assert kwargs["tls"] is True
+    assert kwargs["tls_insecure"] is True

backend/tests/test_zigbee_service.py

@@ -361,3 +361,79 @@ async def test_test_mqtt_connection_failure() -> None:
 
         with pytest.raises(ConnectionError):
             await _test_mqtt_connection("bad-host", 1883)
+
+
+# ---------------------------------------------------------------------------
+# TLS context
+# ---------------------------------------------------------------------------
+
+import ssl  # noqa: E402
+
+from app.services.zigbee_service import _build_tls_context  # noqa: E402
+
+
+def test_build_tls_context_secure_verifies_cert() -> None:
+    ctx = _build_tls_context(insecure=False)
+    assert ctx.check_hostname is True
+    assert ctx.verify_mode == ssl.CERT_REQUIRED
+
+
+def test_build_tls_context_insecure_disables_verification() -> None:
+    ctx = _build_tls_context(insecure=True)
+    assert ctx.check_hostname is False
+    assert ctx.verify_mode == ssl.CERT_NONE
+
+
+@pytest.mark.asyncio
+async def test_test_mqtt_connection_passes_tls_context() -> None:
+    class _FakeClient:
+        async def __aenter__(self):
+            return self
+
+        async def __aexit__(self, *_):
+            pass
+
+    with patch("app.services.zigbee_service.aiomqtt") as mock_aiomqtt:
+        mock_aiomqtt.Client.return_value = _FakeClient()
+        mock_aiomqtt.MqttError = Exception
+
+        await _test_mqtt_connection("host", 8883, tls=True)
+        kwargs = mock_aiomqtt.Client.call_args.kwargs
+        assert kwargs["tls_context"] is not None
+        assert kwargs["tls_context"].verify_mode == ssl.CERT_REQUIRED
+
+
+@pytest.mark.asyncio
+async def test_test_mqtt_connection_no_tls_context_when_disabled() -> None:
+    class _FakeClient:
+        async def __aenter__(self):
+            return self
+
+        async def __aexit__(self, *_):
+            pass
+
+    with patch("app.services.zigbee_service.aiomqtt") as mock_aiomqtt:
+        mock_aiomqtt.Client.return_value = _FakeClient()
+        mock_aiomqtt.MqttError = Exception
+
+        await _test_mqtt_connection("host", 1883, tls=False)
+        assert mock_aiomqtt.Client.call_args.kwargs["tls_context"] is None
+
+
+@pytest.mark.asyncio
+async def test_test_mqtt_connection_insecure_passes_no_verify_context() -> None:
+    class _FakeClient:
+        async def __aenter__(self):
+            return self
+
+        async def __aexit__(self, *_):
+            pass
+
+    with patch("app.services.zigbee_service.aiomqtt") as mock_aiomqtt:
+        mock_aiomqtt.Client.return_value = _FakeClient()
+        mock_aiomqtt.MqttError = Exception
+
+        await _test_mqtt_connection("host", 8883, tls=True, tls_insecure=True)
+        ctx = mock_aiomqtt.Client.call_args.kwargs["tls_context"]
+        assert ctx.verify_mode == ssl.CERT_NONE
+        assert ctx.check_hostname is False