Feature: add connector worker runtime

[smithaldon1]

Summary

• Add a long-running read-only connector worker entrypoint for enabled connection profiles.
• Wire Docker Compose connector-worker to the new runtime and poll interval env.
• Add read-only MQTT source support, OPC UA browse-path resolution, fixture corrections, docs, and learning log updates.

Closes #238

Test Evidence

• .venv/bin/python -m pytest services/ingestion/tests/test_connector_worker.py services/ingestion/tests/test_opcua_read_only_adapter.py services/ingestion/tests/test_mqtt_read_only_adapter.py services/ingestion/tests/test_bacnet_read_only_adapter.py services/simulator/tests/test_docker_compose_runtime_docs.py: 39 passed before final fixture expansion; final focused suite with fixture tests: 49 passed; MQTT focused suite: 12 passed.
• make test-integration: 104 passed, 2 skipped.
• make lint: All checks passed.
• make typecheck: compileall completed successfully.
• make test: 280 passed, 4 skipped.
• docker compose -f infra/docker/docker-compose.yml config: passed.
• Compose smoke with Demo-Factory running separately: connector-worker healthy; logs showed OPC UA profiles=1 records=5 emitted_events=5; Postgres factory_events count reached 20 before cleanup.

Docs Impact

• Updated ingestion README, Docker Compose runtime docs, troubleshooting env list, .env.example, and docs/LEARNING_LOG.md.

Follow-up Work

• MQTT currently records numeric Sparkplug metrics when they arrive; boolean/string metrics are logged as nonnumeric until source-to-event mappings support non-process-measurement event types.
• BACnet remains disabled in the Demo-Factory fixture by default per prior Docker Desktop variability.

[smithaldon1]

Reviewed and approved for merge