Add protocol connection profile schema

[smithaldon1]

Closes #207

Summary

• Add ProtocolConnectionProfile to the shared factory_events contracts package for OPC-UA, MQTT, and BACnet profiles.
• Define common profile metadata, enabled state, endpoint/address, acquisition settings, mapping reference, health state, timestamps, and protocol-specific config blocks.
• Require secret and certificate references instead of raw values, validate protocol/config combinations, and add fixtures for all three protocols.

Test Evidence

• .venv/bin/python -m pytest packages/factory-events/tests/test_connection_profile_contracts.py - passed, 10 tests.
• make test-contract - passed, 76 tests.
• make test - passed, 223 tests.
• make lint - passed.
• make typecheck - passed.
• make docs - passed placeholder docs target: "Docs are Markdown-only in the MVP skeleton; no docs checker is configured yet."
• git diff --check and git diff --cached --check - passed.

Docs Impact

• Updated docs/DATA_CONTRACTS.md with the connection profile contract.
• Updated packages/factory-events/README.md.
• Updated docs/LEARNING_LOG.md.

Follow-up Work

• Implement 3. Feature: Add connection profile API and storage #208 next: connection profile API and storage.
• Keep test-connection behavior, adapters, Workbench forms, and tag/source browsing out of this schema PR.

[smithaldon1]

Reviewed and approved for merge