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_dashboards.py

@@ -2,7 +2,7 @@
 
 import pytest
 
-from app.flow.dashboards import (
+from fluksio.flow.dashboards import (
     DashboardDef,
     DashboardNotFound,
     DashboardStore,
@@ -11,11 +11,11 @@ from app.flow.dashboards import (
     WidgetDef,
     default_dashboard,
 )
-from app.flow.messages import DType, MessageSpec
-from app.flow.nodes import Node
-from app.flow.pipeline import Pipeline
-from app.flow.state import MemoryState
-from app.flow.store import FlowStore, StaleVersion
+from fluksio.flow.messages import DType, MessageSpec
+from fluksio.flow.nodes import Node
+from fluksio.flow.pipeline import Pipeline
+from fluksio.flow.state import MemoryState
+from fluksio.flow.store import FlowStore, StaleVersion
 
 
 @pytest.fixture