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_logs.py

@@ -3,11 +3,11 @@
 import sys
 from typing import Any
 
-from app.flow import logs
-from app.flow.controller import with_settings
-from app.flow.messages import DType, MessageSpec
-from app.flow.nodes import Node
-from app.flow.pipeline import Pipeline
+from fluksio.flow import logs
+from fluksio.flow.controller import with_settings
+from fluksio.flow.messages import DType, MessageSpec
+from fluksio.flow.nodes import Node
+from fluksio.flow.pipeline import Pipeline
 
 
 def run_with_capture(nodes: list[Node], bus: "RecordingBus") -> None: