Add BACnet read-only adapter foundation

[smithaldon1]

Closes #218

Summary

• Add an ingestion-layer BACnet read-only adapter foundation that loads enabled BACnet ProtocolConnectionProfile records from the local profile store.
• Poll configured object references through an injectable BacnetObjectReader; no BACnet writes, commandable-property changes, object discovery, or runtime scheduler is added.
• Support device address, device instance, optional network number, configured object identifiers, polling interval access, units, object names, and object-to-FactoryEvent mapping.
• Normalize numeric BACnet object readings into process.measurement.recorded FactoryEvents with source metadata for connection profile ID, network/device descriptor, object reference, adapter name, and poll index.
• Add clear adapter errors for invalid profile stores, unavailable devices, missing objects, unconfigured objects, stale readings, and nonnumeric values.
• Document Docker Desktop BACnet/UDP demo limitations separately from production BACnet/IP expectations.

Test Evidence

• .venv/bin/python -m pytest services/ingestion/tests/test_bacnet_read_only_adapter.py - passed, 9 tests.
• make test-integration - passed, 94 tests.
• make lint - passed, Ruff found no issues after import cleanup.
• make typecheck - passed, compileall completed across packages and services.
• make test - passed, 266 tests.
• make docs - passed; docs are Markdown-only and no checker is configured yet.
• git diff --check and git diff --cached --check - passed.

Docs Impact

• Updated services/ingestion/README.md with the BACnet read-only adapter foundation, Docker Desktop demo limitations, production BACnet/IP expectations, source metadata behavior, safety boundary, and focused test command.
• Updated docs/LEARNING_LOG.md with what changed, why it matters, how the data flows, how to test it, and the next learning step.

Follow-up Work

• Add a real BACnet/IP object reader only after connector runtime orchestration, network approval, and object mapping rules are defined.
• Add explicit tag/source mapping lookup so object mapping can be governed by mapping_reference instead of adapter defaults and object reader metadata.
• Keep BACnet writes, commandable-property changes, arbitrary object discovery, and UI ingestion controls out of this adapter until dedicated issues and ADR updates define those boundaries.

[smithaldon1]

Reviewed and approved for merge