One image for the whole app: engine, API and dashboard on one port

The backend image now builds the SPA and serves it on the API's own origin
(fluksio/spa.py), so an instance is a single container with no proxy, DNS,
port 80 or .env: `docker compose up -d` with the new compose.yml runs it on
localhost:8080. It starts on fluksio serve (persisted secret key, first
admin printed once) and brings its own Redis when REDIS_HOST is unset.

Slimmer: python:3.13-slim, no dev group, uv once, fastapi without the cloud
CLI. Optional features are per-feature extras (mqtt, influx, email, sentry,
ml, server for all) picked with the EXTRAS build argument; numpy moved to
`ml`. ffmpeg left the image for imageio-ffmpeg via the Modules screen.

The operator stack runs the same image with app. and api. routed to it; the
nginx frontend service, the LAN nginx proxy and DOMAIN in the backend are
gone, and the MCP issuer is FRONTEND_HOST.

docs/code/cli.md

@@ -11,8 +11,9 @@ For the browser dashboard, sign up at [fluksio.com](https://fluksio.com), add
 an instance, then run `fluksio enroll <code>` in the same directory.
 
 Use `fluksio --help` or `fluksio COMMAND --help` for command options.
-`pip install 'fluksio[server]'` adds MQTT, InfluxDB, outbound mail and error
-reporting. A machine that only executes remote nodes can install
+`pip install 'fluksio[server]'` adds MQTT, InfluxDB, outbound mail, error
+reporting and numpy, or name only what you need, such as `fluksio[mqtt]`. A
+machine that only executes remote nodes can install
 [`fluksio-worker`](workers.md).
 
 ## Where an instance lives
@@ -123,7 +124,7 @@ Starts the same agent as the standalone `fluksio-worker` command:
 
 ```sh
 FLUKSIO_WORKER_TOKEN=your-token fluksio worker \
-  --url wss://api.example.com/api/v1/workers/attach --labels gpu
+  --url wss://fluksio.example.com/api/v1/workers/attach --labels gpu
 ```
 
 Create the worker token on the engine first. See [Remote workers](workers.md)
@@ -140,7 +141,7 @@ is a fallback.
 ### `fluksio login`
 
 ```sh
-fluksio login --url https://api.example.com
+fluksio login --url https://fluksio.example.com
 ```
 
 Prompts for credentials and saves an API token for a remote engine.