init: Lobe Sandbox Backend scaffold + host-init + base image build script

- scripts/host-init.sh: 幂等宿主初始化(btrfs pool + project + profile + UFW/iptables 修复)
- images/base/build.sh: Debian13 base 镜像构建脚本
- .memory/project.md: 设计决策、坑点、进度记录

状态: Phase 1 完成, Phase 2 base 镜像构建被 SSH 断开中断,
sb-builder 已 stop 保留,续跑需改 systemd-run 抗 SSH 断开。

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.memory/worklog.json

@@ -27,6 +27,13 @@
       "message": "auto-save 2026-04-18 16:12 (~1)",
       "hash": "380dc95",
       "files_changed": 1
+    },
+    {
+      "ts": "2026-04-18T16:18:17+08:00",
+      "type": "commit",
+      "message": "auto-save 2026-04-18 16:18 (+1, ~1)",
+      "hash": "e9cc9df",
+      "files_changed": 2
     }
   ]
 }