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/flow/test_alerts.py

@@ -6,7 +6,7 @@ from pathlib import Path
 
 import pytest
 
-from app.flow.alerts import (
+from fluksio.flow.alerts import (
     ALERTING_EVENTS,
     FLAP_THRESHOLD,
     RATE_LIMIT,
@@ -17,7 +17,7 @@ from app.flow.alerts import (
     Rule,
     describe,
 )
-from app.flow.events import EventBus
+from fluksio.flow.events import EventBus
 
 
 class Clock: