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>

stacks/sql/README.md

@@ -1,11 +1,9 @@
 # sql
 
-Central configuration database — the "single point of config" backing Keycloak, Gitea, and other stacks that need a relational store. **Cloud-only stack.**
+Central configuration database — the "single point of config" backing Keycloak, Gitea, MLflow, and any stack that needs a relational store. **Cloud-only.**
 
+- **Engine**: postgres 16-alpine
 - **Network**: `data` only (no internet egress)
-- **Engine**: stub uses **postgres:16-alpine** pending decision (postgres vs mariadb vs mysql)
-- **Volume**: `sql-data`
-- **TODO**:
-  - confirm engine choice (likely postgres for keycloak + gitea compatibility)
-  - per-app database/role provisioning (init scripts in `config/init.d/`)
-  - backup strategy (pg_dump cron sidecar vs streaming replica)
+- **Volume**: `sql-data` (PGDATA)
+- **Init scripts**: `config/init.d/*.sql` runs on first start — provisions per-app databases/roles (gitea, keycloak, mlflow, …)
+- **TODO**: backup strategy (pg_dump cron sidecar vs streaming replica)

stacks/sql/compose.yml

@@ -1,6 +1,5 @@
-# sql — single point of config DB (cloud only)
+# sql — central config DB (postgres, cloud only)
 # Networks: data (no internet egress)
-# TBD: postgres / mariadb / mysql — stub uses postgres pending decision
 
 services:
   sql:
@@ -14,6 +13,7 @@ services:
       TZ: ${TZ:-Europe/Amsterdam}
     volumes:
       - sql-data:/var/lib/postgresql/data
+      - ./config/init.d:/docker-entrypoint-initdb.d:ro
 
 networks:
   data: