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>

.gitea/workflows/pre-commit.yml

@@ -49,5 +49,5 @@ jobs:
       # The hooks cover ruff and biome but not mypy, which `make lint-backend`
       # runs and which is strict for everything outside the flow prototypes.
       - name: Typecheck backend
-        run: uv run mypy app
+        run: uv run mypy fluksio
         working-directory: backend