chore: upgrade to 3.1.0+v2.0.0

Minor bump — no operator action required (Postgres/ClickHouse changes are automatic).

- Postgres: use pgautoupgrade/pgautoupgrade:18-alpine in place of the custom
  pg_upgrade entrypoint. The existing cluster is upgraded in place automatically
  on deploy; PGDATA pinned to the legacy path; adds a pg_isready healthcheck.
  Removes entrypoint.postgres.sh.tmpl and DB_ENTRYPOINT_VERSION.
- ClickHouse backup fetch: cache the clickhouse-backup binary on the persistent
  volume and retry with backoff to avoid the download crash-loop. The tool is
  required — if it can't be installed after retries the entrypoint aborts and
  the server does not start, rather than coming up without backup/restore.
- Add CLICKHOUSE_DATABASE_URL; bump the clickhouse entrypoint config version.
- Remove a stray broken link reference in the README.

compose.yml

@@ -12,6 +12,7 @@ services:
       - BASE_URL=https://$DOMAIN
       - SECRET_KEY_BASE
       - DATABASE_URL=postgres://plausible:plausible@${STACK_NAME}_db:5432/plausible
+      - CLICKHOUSE_DATABASE_URL=http://${STACK_NAME}_plausible_events_db:8123/plausible_events_db
       - SMTP_HOST_ADDR
       - MAILER_EMAIL
       - SMTP_HOST_PORT
@@ -32,23 +33,24 @@ services:
         - "traefik.http.routers.${STACK_NAME}.rule=Host(`${DOMAIN}`${EXTRA_DOMAINS})"
         - "traefik.http.routers.${STACK_NAME}.entrypoints=web-secure"
         - "traefik.http.routers.${STACK_NAME}.tls.certresolver=${LETS_ENCRYPT_ENV}"
-        - coop-cloud.${STACK_NAME}.version=3.0.1+v2.0.0
+        - coop-cloud.${STACK_NAME}.version=3.1.0+v2.0.0
   db:
-    image: postgres:13.12
-    configs:
-      - source: db_entrypoint
-        target: /docker-entrypoint.sh
-        mode: 0555
-    # Custom docker entrypoint to handle major Postgres version upgrades
+    image: pgautoupgrade/pgautoupgrade:18-alpine
     volumes:
       - db-data:/var/lib/postgresql/data
-    entrypoint: /docker-entrypoint.sh
     environment:
+      # pin legacy PGDATA so the existing cluster on the volume is upgraded in place, not re-init'd
+      - PGDATA=/var/lib/postgresql/data
       - POSTGRES_USER=plausible
       - POSTGRES_PASSWORD=plausible
       - POSTGRES_DB=plausible
     networks:
       - internal
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U plausible -d plausible"]
+      interval: 5s
+      timeout: 5s
+      retries: 60
     deploy:
       labels:
         backupbot.backup: "true"
@@ -98,10 +100,6 @@ configs:
   clickhouse-user-config:
     name: ${STACK_NAME}_clickhouse_user_config_${CLICKHOUSE_USER_CONF_VERSION}
     file: clickhouse-user-config.xml
-  db_entrypoint:
-    name: ${STACK_NAME}_db_entrypoint_${DB_ENTRYPOINT_VERSION}
-    file: entrypoint.postgres.sh.tmpl
-    template_driver: golang
   clickhouse_entrypoint:
     name: ${STACK_NAME}_clickhouse_entrypoint_${CLICKHOUSE_ENTRYPOINT_VERSION}
     file: entrypoint.clickhouse.sh