Rename the workspace layout: fluksio -> app, website -> index

The repo moves to git.stroblme.de:Fluksio/app.git and its sibling to
Fluksio/index.git, so every cross-repo path reference moves with it. The
architecture sources the roadmap cites now live in the docs repo under
architecture/, and the brand marks in the index repo's src/assets.

Also replaces the placeholder README with one that reflects the actual layout.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

README.md

@@ -1,3 +1,42 @@
-# Fluksio Main Repository
+# Fluksio App
 
-A node based, test-driven home-automation software to built to scale.
+The core of Fluksio: a node-based, test-driven automation software built to scale. This
+repo holds the FastAPI backend, the flow engine, and the dashboard SPA. It is served on
+`app.${DOMAIN}` (SPA) and `api.${DOMAIN}` (API); the marketing site lives in the sibling
+`index` repo.
+
+## Layout
+
+```text
+backend/        FastAPI + SQLModel + Alembic + Postgres
+  app/flow/     the flow engine (nodes, pipeline, state backends, controller)
+frontend/       React 19 + TanStack Router + Tailwind 4 + shadcn/ui
+docker/         compose.yml → compose.dev.yml → compose.local.yml (+ compose.traefik.yml)
+scripts/        generate-client.sh, test.sh
+```
+
+## Getting started
+
+Normally driven from the workspace root (`make init` once, then `make dev`). Standalone:
+
+```sh
+make install       # uv sync + bun install
+make dev-utils     # db, adminer, proxy, mailcatcher, prestart only
+make dev-backend   # FastAPI on :8000, hot reload
+make dev-frontend  # Vite on :5173
+```
+
+```sh
+make test           # pytest + Playwright
+make lint           # ruff + mypy + biome
+make generate-client  # regenerate the frontend SDK from the OpenAPI schema
+```
+
+`make help` lists every target.
+
+## Documentation
+
+- [`ROADMAP.md`](ROADMAP.md) — strategy and feature record
+- [`NOTEPAD.md`](NOTEPAD.md) — deferred work and findings
+- [`DESIGN.md`](DESIGN.md) — points at the workspace root's `DESIGN-GUIDELINES.md`
+- `docs/architecture/` in the sibling `docs` repo — the requirement sources