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_vocabulary.py

@@ -4,10 +4,17 @@ These are the shapes a Node-RED installation is mostly made of, so their
 behaviour is worth pinning rather than just their construction.
 """
 
-from app.flow.messages import DType, MessageSpec
-from app.flow.nodes import ChangeNode, ExecNode, FileNode, JoinNode, RbeNode, SwitchNode
-from app.flow.pipeline import Pipeline
-from app.flow.state import MemoryState
+from fluksio.flow.messages import DType, MessageSpec
+from fluksio.flow.nodes import (
+    ChangeNode,
+    ExecNode,
+    FileNode,
+    JoinNode,
+    RbeNode,
+    SwitchNode,
+)
+from fluksio.flow.pipeline import Pipeline
+from fluksio.flow.state import MemoryState
 
 
 def spec(name: str, dtype: DType = DType.FLOAT) -> MessageSpec:
@@ -233,7 +240,7 @@ def test_a_file_node_refuses_to_leave_its_directory():
 
 
 def test_a_file_round_trips_through_the_sandbox(tmp_path, monkeypatch):
-    from app.core.config import settings
+    from fluksio.core.config import settings
 
     monkeypatch.setattr(settings, "FLOWS_DIR", tmp_path / "flows")