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/fluksio/cloud/__init__.py

@@ -0,0 +1,6 @@
+"""Optional remote access through a Fluksio portal.
+
+Nothing in here runs unless someone enrolled this installation: with no
+``cloud.json`` the connector never starts and the portal's tokens are refused
+like any other bad credential. Turning it off is deleting that one file.
+"""