SIENTIAPDE-1811

Enhance OPC UA testing framework and documentation

- Added a new marker in pyproject.toml for tests using the in-process OPC UA server.
- Updated opc-communication.md to clarify E2E test scenarios involving the real OPC server and mock server.
- Introduced an in-process asyncua OPC UA server fixture in conftest.py for E2E tests.
- Created a new fixture for activities using the real OpcRepository connected to the in-process server.
- Updated scenarios.md to include instructions for running OPC real-server tests.

docs/opc-communication.md

@@ -157,4 +157,6 @@ Legacy activity metrics: `laborious_prediction_opc_writing_count`, `laborious_pr
 
 - Unit: [`tests/laborious/utils/repository/test_opc_repository.py`](../tests/laborious/utils/repository/test_opc_repository.py)
 - Unit: [`tests/laborious/activities/test_opc.py`](../tests/laborious/activities/test_opc.py)
-- E2E: [`e2e/test_predictions_batch_format_export.py`](../e2e/test_predictions_batch_format_export.py), scenarios in [`e2e/scenarios.md`](../e2e/scenarios.md)
+- E2E (mock OPC): [`e2e/test_predictions_batch_format_export.py`](../e2e/test_predictions_batch_format_export.py)
+- E2E (in-process asyncua server + real `OpcRepository`): [`e2e/test_opc_real_server.py`](../e2e/test_opc_real_server.py) — scenarios 3.1.2, 3.2.2, 3.2.4, 3.2.5
+- Scenarios: [`e2e/scenarios.md`](../e2e/scenarios.md)