feat: add public Docker deployment stack

.env.example

@@ -0,0 +1,42 @@
+# Public endpoint. Caddy obtains TLS certificates for DOMAIN automatically.
+DOMAIN=game.example.com
+PUBLIC_SCHEME=https
+ACME_EMAIL=admin@example.com
+HTTP_PORT=80
+HTTPS_PORT=443
+
+# Core2026 source. A public HTTPS URL needs no extra credential.
+CORE_REPOSITORY_URL=https://github.com/your-org/core2026.git
+CORE_BOOTSTRAP_REF=main
+
+# Development bind override (used only with compose.dev.yaml).
+# CORE_DEV_PATH=../core2026
+# DEV_UID=1000
+# DEV_GID=1000
+
+# Persistent services. Use long random values; do not commit .env.
+POSTGRES_DB=sammo
+POSTGRES_USER=sammo
+POSTGRES_PASSWORD=replace-with-a-long-random-database-password
+REDIS_PASSWORD=replace-with-a-long-random-redis-password
+GAME_TOKEN_SECRET=replace-with-at-least-32-random-bytes
+GATEWAY_BOOTSTRAP_TOKEN=replace-with-a-separate-random-bootstrap-token
+
+# The first startup creates this superuser only when the user table is empty.
+INITIAL_ADMIN_USERNAME=admin
+INITIAL_ADMIN_PASSWORD=replace-with-a-long-random-admin-password
+INITIAL_ADMIN_DISPLAY_NAME=Administrator
+
+# Kakao Developers app values. Register https://DOMAIN/gateway/oauth/callback.
+KAKAO_REST_KEY=replace-with-kakao-rest-api-key
+KAKAO_ADMIN_KEY=
+
+# Account policy and optional compatibility secret.
+GATEWAY_LOCAL_REGISTRATION_ENABLED=true
+GATEWAY_ADMIN_LOCAL_ACCOUNT_ENABLED=true
+GATEWAY_LOCAL_ACCOUNT_GRACE_DAYS=7
+GATEWAY_LEGACY_PASSWORD_GLOBAL_SALT=
+
+# Initial stopped profile inventory. Each deployment can choose its own branch in the Admin GUI.
+BOOTSTRAP_PROFILES=gateway,che,kwe,pwe,twe,nya,pya,hwe
+TZ=Asia/Seoul