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_pipeline.py

@@ -1,9 +1,9 @@
 """The wiring fundamentals: name binding, fan-in, namespaces, validation."""
 
-from app.flow.events import EventBus
-from app.flow.messages import DType, MessageSpec
-from app.flow.nodes import Node
-from app.flow.pipeline import Pipeline
+from fluksio.flow.events import EventBus
+from fluksio.flow.messages import DType, MessageSpec
+from fluksio.flow.nodes import Node
+from fluksio.flow.pipeline import Pipeline
 
 
 def spec(name: str, dtype: DType = DType.FLOAT, port: str = "") -> MessageSpec: