fix(stack): bring-up fixes from first local deployment

- traefik pin v3.3 -> v3.6: v3.3's old docker client fails against
  Engine 29 socket proxy (empty daemon errors, no routers)
- backend/minio/chatbot/umami: traefik.docker.network hint — Traefik
  picked the internal-network IP for multi-network services and replies
  were hairpin-dropped (all backend routes hung)
- db-init: psql needs an explicit -d arameshplaza (no default db 'aramesh'),
  set -e so failures actually fail; one-shot folded-YAML needs semicolons
- chatbot image: drop g++ (apt unreachable in build network; all wheels
  prebuilt) and mkdir /data before chown (VOLUME does not create it)
- frontend image: create caddy user (alpine image has none) with writable
  /config and /data
- monitoring: blackbox probes replace raw metric scrapes of JSON/HTML
  health endpoints (they reported 'down' while healthy); blackbox joins
  edge; SITE_URL passed via env (Prometheus has no ${VAR:-default}
  expansion); ContainerMemoryNearLimit PromQL fixed (comparison inside
  label braces); HostDiskAlmostFull filters WSL/Docker-Desktop
  pseudo-mounts
- alertmanager: config rendered by stack.sh (no env expansion in AM) and
  delivered to Bale (tapi.bale.ai); stack.sh monitoring command
- machine-local override: minio console/API moved to 29001/29000

frontend/Dockerfile

@@ -4,6 +4,13 @@
 
 FROM caddy:2-alpine
 
+# نسخهٔ alpine کاربر caddy ندارد — اینجا ساخته می‌شود؛ /config و /data مسیرهای
+# storage سی‌دی هستند و باید برای کاربر نوشتنی باشند
+RUN addgroup -S caddy \
+    && adduser -S -G caddy -s /sbin/nologin caddy \
+    && mkdir -p /config /data \
+    && chown -R caddy:caddy /config /data
+
 COPY Caddyfile /etc/caddy/Caddyfile
 COPY --chown=caddy:caddy dist /srv