fix(tests): import all models in conftest so create_all sees the full schema

The test_db fixture calls Base.metadata.create_all on a fresh test DB.
That only creates tables for models that have been imported (and thus
registered with Base.metadata) by the time the fixture runs.

app.main imports app.core.database (which gives us Base) but does NOT
eagerly import the model modules — most are pulled in lazily inside
scheduler functions (archive_stale_ai_sessions etc.) and route
modules. At fixture-setup time, only the handful of models touched by
those eager imports are on the metadata, so any test that exercises
PSA, network diagrams, ratings, escalations, etc. fails with
\`UndefinedTableError: relation "X" does not exist\` and a cascade of
500s on every endpoint that queries the missing table.

Adding \`from app import models as _models\` (rather than the bare
\`import app.models\` which would shadow the \`app\` FastAPI instance
imported just above) pulls in app/models/__init__.py, which itself
imports every model module — registering all ~60 tables with
Base.metadata before create_all runs.

Verified locally: tests/test_psa_writeback_phase4.py went from
1 failed / 6 errors → 4 failed / 3 passed (the cascading errors were
masking the actual passes).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/tests/conftest.py

@@ -16,6 +16,14 @@ from app.main import app
 from app.core.database import Base, get_db
 from app.core.admin_database import get_admin_db
 from app.core.config import settings
+# Import every model module so all tables are registered with Base.metadata
+# before the test_db fixture calls create_all. app.main imports models lazily
+# (inside scheduler functions and route modules), which is fine at runtime
+# but leaves the metadata incomplete at fixture-setup time — surfacing as
+# "relation X does not exist" errors for any model whose route/scheduler
+# hasn't been loaded yet. The `from app import models` form avoids
+# shadowing the `app` FastAPI instance imported just above.
+from app import models as _models  # noqa: F401
 
 # Disable invite code requirement for tests
 settings.REQUIRE_INVITE_CODE = False