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/crud/test_user.py

@@ -2,9 +2,9 @@ from fastapi.encoders import jsonable_encoder
 from pwdlib.hashers.bcrypt import BcryptHasher
 from sqlmodel import Session
 
-from app import crud
-from app.core.security import verify_password
-from app.models import User, UserCreate, UserUpdate
+from fluksio import crud
+from fluksio.core.security import verify_password
+from fluksio.models import User, UserCreate, UserUpdate
 from tests.utils.utils import random_email, random_lower_string