fix(install): backups exist on a default install; retention resolves real world dirs (#6)

Three faces of one gap, all on the supported install path:

- Backup/restore answered 503 out of the box: nothing ever rendered the
  archive PVC, so FELIS_BACKUP_PVC was unset. The bundle now renders the
  PVC (Minecraft namespace, RWO 10Gi, cluster default class) and
  'felis manifests' names it by default (--backup-pvc= is the explicit
  no-store shape); bootstrap passes it through so the generated felis.toml
  [archive] local_path and the jobs' mount path come from one variable.
- Retention was unreachable: bootstrap never passed the reaper flags. It
  now forwards FELIS_WORLDS_HOST_PATH/FELIS_ARCHIVE_LOCAL_PATH, so one
  env enables the daily CronJob; unset keeps today's fail-safe (no reaper,
  nothing deleted).
- Even when enabled it could not find a world on a stock install:
  resolveWorldDir now also resolves the exact local-path directory
  <pv-name>_<ns>_<pvc-name> read from the live PVC's volumeName (never a
  glob, so a stale deleted PV's bytes can't be archived in place of the
  current world). Reaper Role gains persistentvolumeclaims:get (weaker
  than the delete it already held).

README (zh/en) stops promising automatic/scheduled backups and states
retention is opt-in. bootstrap_test covers the env->flag contract.

README.md

@@ -17,8 +17,8 @@ A Kubernetes-driven Minecraft server hosting platform — one command to deploy,
 
 - **即开即玩**：玩家尝试连接时自动唤醒服务器，空闲后自动休眠，像游戏主机一样省资源。
 - **Web 控制面板**：浏览器中查看服务器状态、在线玩家与资源用量，管理备份与恢复。
-- **自动备份与恢复**：定时将世界打包存档，支持从任意备份点一键回滚。
-- **智慧回收**：超过 15 天无人游玩的世界自动备份后删除，释放磁盘空间。
+- **备份与恢复**：一键把世界打包进集群内的归档库，支持从任意备份点回滚；默认安装就已启用（归档 PVC 与路径由安装器一并生成）。
+- **智慧回收（可选开启）**：超过 15 天无人游玩的世界自动备份后删除，释放磁盘空间；安装时设置 `FELIS_WORLDS_HOST_PATH`（k3s 默认 `/var/lib/rancher/k3s/storage`）即启用每日回收，不设置则不删任何世界。
 - **多核心支持**：兼容 Paper、Fabric、Forge、NeoForge，经由 Velocity 代理统一入口。
 - **模组自助提交**：玩家自行上传模组包，服主审批通过后自动构建并部署。
 - **Passkey 登录**：支持指纹、面容、硬件密钥等无密码认证方式。