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>

ROADMAP.md

@@ -44,14 +44,14 @@ Python, optimised for development speed. Owns the graph structure, persistence a
 external interfaces. See `docs/architecture/structure.canvas` → *Backend – Management*.
 
 - [x] FastAPI + SQLModel + Alembic + Postgres base with JWT auth and user management
-- [x] Flow engine in `backend/app/flow/`: `Node` / `Pipeline` / `StateBackend`
+- [x] Flow engine in `backend/fluksio/flow/`: `Node` / `Pipeline` / `StateBackend`
       (memory + Redis) / `FlowController`
 - [x] Node types: HTTP, MQTT, InfluxDB, Delay, MLP
 - [x] Flow-logic vocabulary as node types rather than repeated code: inject (manual,
       interval, cron or at startup), switch, change, filter-unchanged, join, trigger,
       command, file and ntfy. Each is configured by filling in a form the editor
       generates from its parameter schema
-- [x] `app/flow` is an importable package with absolute `app.flow.*` imports
+- [x] `fluksio/flow` is an importable package with absolute `fluksio.flow.*` imports
 - [x] Typed, serializable node I/O: every port declares a `DType`, messages are
       JSON on the wire and in Redis, no pickle anywhere. Binary codecs are still
       open — `DType.JSON` carries everything non-scalar for now