Collapse the three data layers into one. app/db.py now exposes a single
Base, a cached engine bound to app_database_url with SQLite WAL enabled, and
get_engine/get_session_local/reset_db_caches/get_db_session. Delete
app/auth_db.py, app/poo_db.py and app/models/base.py. All models (auth,
config, public_ip, location, poo) inherit the one Base and register on a
single metadata. Dependencies converge to a single get_db; all routes use it.
Also update the alembic env.py files (app/location/poo) and tests that
imported the removed modules so the suite stays green, and drop the obsolete
test_legacy_style_location_db test whose flow (app reading a separate location
DB) no longer exists. Location/poo Alembic chains, adopt scripts and adoption
tests remain for M1-T04; config fields remain for M1-T05.
pytest 109 passed; ruff clean (pre-existing only); WAL verified; single
Base.metadata holds all seven tables.
Add alembic_app revision 20260611_06_merge_location_poo_tables that builds
empty location and poo_records tables (REAL float columns, matching the
production schema and the adopt scripts' EXPECTED_*_TABLE_INFO constants).
Update APP_BASELINE_REVISION to the new head. Schema-only; data migration
is handled separately by scripts/migrate_legacy_data.py (M1-T02).
tliu93