Adds tests/test_pr8_metadata_registration.py: opens a fresh SQLite
engine via init_engine() and asserts inspect(conn).get_table_names()
contains service_accounts, api_keys, and external_users. Guards
against an ORM row class being added under deerflow/persistence/* but
accidentally left out of deerflow/persistence/models/__init__.py —
which would leave the table un-provisioned at startup and surface as
a confusing "no such table" later in Stage 1.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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