Rebuild deploy process on the project template

- Dockerfile: deps → builder → pb-downloader → runner stages, cross-arch
  (BUILDPLATFORM node stages, TARGETARCH PocketBase binary), Debian slim
  runner, VOLUME /app/pb_data, dual healthcheck, docker-entrypoint.sh
- docker-entrypoint.sh: bash supervisor replacing scripts/run-all.mjs
- Makefile: build-production (multi-arch push from git remote),
  build-check, build-check-local
- deploy.sh [tag]: make build-production then ansible-playbook with tag
- drop .env/.env.example (credentials live in ansible/vars/default.yml)

.env.example

@@ -1,8 +0,0 @@
-# Copy to .env and fill in real values. .env is git-ignored.
-REGISTRY=registry.tanshu.com
-REGISTRY_USER=ta-registry
-REGISTRY_PASSWORD=changeme
-
-# Initial PocketBase admin (applied on first container start; idempotent)
-PB_SUPERUSER_EMAIL=admin@greatbear.in
-PB_SUPERUSER_PASSWORD=changeme