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/compose.yml

@@ -4,20 +4,29 @@
 
 name: cloud
 
-# Uncomment includes as each stack is scaffolded with real services.
+# Uncomment includes as each stack is hardened beyond stub.
 include:
+  # Core ingress + identity
   # - ../stacks/nginx-proxy/compose.yml
   # - ../stacks/wireguard-server/compose.yml
   # - ../stacks/keycloak/compose.yml
   # - ../stacks/portainer/compose.yml
+  # Data
+  # - ../stacks/sql/compose.yml
   # - ../stacks/influxdb/compose.yml
-  # - ../stacks/grafana/compose.yml
+  # Apps
   # - ../stacks/node-red/compose.yml
-  # - ../stacks/mqtt/compose.yml
-  # - ../stacks/postfix/compose.yml
+  # - ../stacks/grafana/compose.yml
   # - ../stacks/gitea/compose.yml
   # - ../stacks/jenkins/compose.yml
-  # - ../stacks/sql/compose.yml
+  # Messaging + mail
+  # - ../stacks/rabbitmq/compose.yml
+  # - ../stacks/postfix/compose.yml
+  # ML / notebooks
+  # - ../stacks/mlflow/compose.yml
+  # - ../stacks/jupyterhub/compose.yml
+  # FROST (when deployed)
+  # - ../stacks/mosquitto/compose.yml
 
 networks:
   edge:
@@ -29,7 +38,7 @@ networks:
   data:
     name: cloud-data
     driver: bridge
-    internal: true     # databases — no internet egress
+    internal: true      # databases — no internet egress
   mgmt:
     name: cloud-mgmt
     driver: bridge