feat: SQL=postgres, nginx+certbot, MQTT split, ML stacks, gitea HTTPS-only, gemaal1 site

Round-2 changes locking in scaffold-phase decisions and adding ML/notebook stacks.

Locked decisions
- sql: postgres 16-alpine (was TBD); init.d/ mount for per-app DB provisioning
- nginx-proxy: stock nginx + certbot sidecar (was nginx:alpine TODO).
  Chose stock over nginxproxy/nginx-proxy because stream{} is required for
  MQTT-TLS reverse-proxy on tcp/8883 to rabbitmq:1883.
- gitea: HTTPS-only (DISABLE_SSH=true). No SSH port published.

MQTT split
- Remove stacks/mqtt placeholder.
- Add stacks/rabbitmq — general-purpose broker (AMQP + MQTT plugin),
  used at both cloud and edge. External MQTT clients reach cloud broker
  via nginx stream-proxy on 8883.
- Add stacks/mosquitto — reserved for the FROST (SensorThings) stack
  only. Cloud-only. Internal to its own stack; no external ingress.

ML / notebooks (cloud-only)
- stacks/mlflow — experiment tracking + model registry. Postgres backend
  on sql stack; local volume for artifacts (S3/MinIO is a TODO).
- stacks/jupyterhub — multi-user notebook server. DockerSpawner via
  mounted docker.sock; users spawn into cloud-app network so they can
  reach mlflow, influxdb (via grafana), rabbitmq.

Sites
- sites/gemaal1 — first edge deployment scaffold. Site-local override
  template for binding nginx to PLANT_LAN_IP.

Docs
- README + docs/architecture.md updated: stacks table now lists 15 stacks,
  ingress + attachment tables reflect mlflow/jupyterhub, TLS strategy
  section locked, MQTT-split section added, Gitea HTTPS-only noted.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

cloud/.env.example

@@ -6,6 +6,7 @@ TZ=Europe/Amsterdam
 # Domain / TLS
 PRIMARY_DOMAIN=
 LETSENCRYPT_EMAIL=
+ACME_CA_URI=https://acme-v02.api.letsencrypt.org/directory
 
 # WireGuard server
 WG_SERVER_PORT=51820
@@ -14,6 +15,7 @@ WG_SERVER_PUBLIC_HOST=
 # Keycloak (admin bootstrap)
 KEYCLOAK_ADMIN=admin
 KEYCLOAK_ADMIN_PASSWORD=
+KEYCLOAK_HOSTNAME=
 
 # InfluxDB
 INFLUX_ADMIN_USER=admin
@@ -25,19 +27,38 @@ INFLUX_BUCKET=telemetry
 # Grafana
 GRAFANA_ADMIN_USER=admin
 GRAFANA_ADMIN_PASSWORD=
+GRAFANA_ROOT_URL=
 
-# SQL (single point of config)
+# SQL (postgres — single point of config)
 SQL_DB=config
 SQL_USER=config
 SQL_PASSWORD=
 
+# RabbitMQ
+RABBITMQ_USER=admin
+RABBITMQ_PASSWORD=
+RABBITMQ_VHOST=/
+
 # Postfix
 POSTFIX_RELAYHOST=
 POSTFIX_FROM_DOMAIN=
 
-# Gitea
+# Gitea (HTTPS-only; uses sql backend)
 GITEA_ROOT_URL=
+GITEA_DB_HOST=sql:5432
+GITEA_DB_NAME=gitea
+GITEA_DB_USER=gitea
+GITEA_DB_PASSWORD=
 
 # Jenkins
 JENKINS_ADMIN_USER=admin
 JENKINS_ADMIN_PASSWORD=
+
+# MLflow (uses sql backend)
+MLFLOW_DB_NAME=mlflow
+MLFLOW_DB_USER=mlflow
+MLFLOW_DB_PASSWORD=
+
+# JupyterHub
+JUPYTER_NOTEBOOK_IMAGE=jupyter/datascience-notebook:latest
+JUPYTERHUB_ADMIN_USERS=