feat(ops): W4-B single-container packaging, DATA_DIR, backup/restore

- DATA_DIR (/data: agent-sessions, backups, exports, tmp); entrypoint chowns it
  to PUID/PGID then drops privileges via gosu; /app binary stays root read-only
- compile with --allow-read --allow-write so mounted library roots are writable
- preflight: DATA_DIR/session dir must be writable (fatal); enabled library
  roots and downloader path mappings checked read/write (warn + audit)
- --role export-mappings (mapping manifest JSON, --compare row counts) and
  --role read-only-on (automation.readOnlyReconcile=true + audit)
- scripts/backup.sh (pg_dump custom + mappings + agent sessions, SHA256SUMS,
  BACKUP_KEEP rotation) and scripts/restore.sh (checksum, refuses with live
  connections, psql single-transaction replay compatible with PG16, read-only
  reconcile on, row-count verification)
- compose: app + postgres only, data volume, env example with key generation
- docs: runbook deploy.md, backup-restore.md with verification record

Co-Authored-By: Claude Opus 5.5 <[email protected]>

docker/compose.env.example

@@ -0,0 +1,22 @@
+# docker compose 用的环境变量(复制为部署目录下的 .env)。
+#
+# SECRET_MASTER_KEY:凭证加密主密钥,生成一次后永不更换(换了之前存的站点/下载器/模型密钥全部无法解密)。
+#   生成:openssl rand -hex 32
+#   必须与数据库备份分开保管(密码管理器 / 离线介质);备份里不含它,丢了它备份里的密钥也无法恢复。
+SECRET_MASTER_KEY=
+# 数据库密码:openssl rand -hex 16
+POSTGRES_PASSWORD=
+
+# 对外端口与绑定地址(放在反代后面时可改成 127.0.0.1)
+UMT_PORT=4380
+UMT_BIND=0.0.0.0
+
+# 容器运行用户:与宿主媒体目录属主一致,例如 id -u / id -g 的输出
+PUID=10001
+PGID=10001
+
+# 备份保留份数(0 = 不轮转)
+BACKUP_KEEP=14
+LOG_LEVEL=info
+# APP_VERSION=v0.1.0
+# 国内网络构建换源(可选):APT_MIRROR=mirrors.ustc.edu.cn