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>

Makefile

@@ -83,7 +83,7 @@ install:  ## Install all dependencies (backend + frontend)
 	cd frontend && bun install
 
 dev-backend:  ## Start the FastAPI backend with hot-reload (local)
-	cd backend && uv run fastapi dev app/main.py
+	cd backend && uv run fastapi dev fluksio/main.py
 
 dev-frontend:  ## Start the Vite dev server (local)
 	cd frontend && bun dev
@@ -169,7 +169,7 @@ lint: lint-backend lint-frontend  ## Run all linters
 lint-backend:  ## Lint backend with ruff + mypy
 	cd backend && uv run ruff check .
 	cd backend && uv run ruff format --check .
-	cd backend && uv run mypy app
+	cd backend && uv run mypy fluksio
 
 lint-frontend:  ## Lint frontend with biome
 	cd frontend && bun run lint