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/tests/utils/user.py

@@ -1,9 +1,9 @@
 from fastapi.testclient import TestClient
 from sqlmodel import Session
 
-from app import crud
-from app.core.config import settings
-from app.models import User, UserCreate, UserUpdate
+from fluksio import crud
+from fluksio.core.config import settings
+from fluksio.models import User, UserCreate, UserUpdate
 from tests.utils.utils import random_email, random_lower_string