Rename the import package app to fluksio

A wheel whose top-level module is `app` collides with anything else in a
user's venv, so the package that is about to be published takes the name
it is published under. Only the Python package moves; the repo, the
Docker WORKDIR and the compose project keep theirs.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

backend/fluksio/core/db.py

@@ -0,0 +1,35 @@
+from sqlmodel import Session, create_engine, select
+
+from fluksio import crud
+from fluksio.core.config import settings
+from fluksio.models import User, UserCreate
+
+# A connection idle across a Postgres restart is dead but still pooled; the
+# pre-ping spends a round trip to find out instead of failing the request.
+engine = create_engine(str(settings.SQLALCHEMY_DATABASE_URI), pool_pre_ping=True)
+
+
+# make sure all SQLModel models are imported (app.models) before initializing DB
+# otherwise, SQLModel might fail to initialize relationships properly
+# for more details: https://github.com/fastapi/full-stack-fastapi-template/issues/28
+
+
+def init_db(session: Session) -> None:
+    # Tables should be created with Alembic migrations
+    # But if you don't want to use migrations, create
+    # the tables un-commenting the next lines
+    # from sqlmodel import SQLModel
+
+    # This works because the models are already imported and registered from app.models
+    # SQLModel.metadata.create_all(engine)
+
+    user = session.exec(
+        select(User).where(User.email == settings.FIRST_SUPERUSER)
+    ).first()
+    if not user:
+        user_in = UserCreate(
+            email=settings.FIRST_SUPERUSER,
+            password=settings.FIRST_SUPERUSER_PASSWORD,
+            is_superuser=True,
+        )
+        user = crud.create_user(session=session, user_create=user_in)