feat(hermes): emit pending approval events

[selvalabs]

Summary

• Emits a Hermes admin_approval_pending event when a new resident registration is created with notifications_approved=false.
• Adds admin_approval_pending to the Hermes event catalog.
• Covers the registration flow with API-level test coverage.

Scope

• Audit/event only: no Telegram, WhatsApp, webhook, deploy, credentials, or LLM calls.

Validation

• uv run pytest tests/unit/test_users_api.py::test_create_user_emits_pending_approval_hermes_event -q
• uv run pytest tests/unit/test_users_api.py tests/unit/test_hermes_catalog.py -q
• uv run ruff check .
• uv run mypy src
• uv run pytest

Closes #42
Refs #37