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/api/routes/test_alerts.py

@@ -5,8 +5,8 @@ from typing import Any
 import pytest
 from fastapi.testclient import TestClient
 
-from app.core.config import settings
-from app.flow.alerts import AlertsConfig, Channel
+from fluksio.core.config import settings
+from fluksio.flow.alerts import AlertsConfig, Channel
 
 PREFIX = f"{settings.API_V1_STR}/alerts"