Add connection profile API and storage

[smithaldon1]

Closes #208

Summary

• Add local JSON-backed connection profile storage for the API service.
• Add CRUD-style profile endpoints: create, list, detail, update, disable, and delete.
• Validate requests with the shared ProtocolConnectionProfile schema before storage.
• Redact secret and certificate reference names in browser-facing responses and sanitize request-validation errors so rejected raw secret-shaped inputs are not echoed.
• Keep profile management separate from protocol ingestion; creating a profile does not start polling or subscriptions.

Test Evidence

• .venv/bin/python -m pytest services/api/tests/test_connection_profiles_api.py - passed, 9 tests.
• make test-integration - passed, 60 tests. First sandboxed run failed because the existing OPC UA worker test could not bind 127.0.0.1; rerun with loopback permission passed.
• make test - passed, 232 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 services/api/README.md with endpoints and FACTORY_CONNECTION_PROFILES_STORE.
• Updated docs/DATA_CONTRACTS.md with API contract notes.
• Updated docs/LEARNING_LOG.md.

Follow-up Work

• Implement 4. Feature: Add read-only connection test endpoint with redacted results #209 next: read-only test-connection API.
• Keep protocol adapters, Workbench forms, diagnostics pages, and tag/source browsing out of this API/storage PR.

[smithaldon1]

Reviewed and approved for merge