dsh-backup: Backup, Restore, and Verify for DeepSeek Harness's `~/.dsh`

dsh-backup is a DeepSeek Harness (DSH) plugin maintained by xiaoyuyu6420, designed to back up and restore user data under `~/.dsh`. It supports macOS, Linux, and Windows 10+, requiring DSH version 0.1.1-rc.2 or a compatible version. Key features include manual backups via the `/backup` command, scheduled automatic backups, SHA256 checksum generation for integrity verification, a rotation policy that retains the last 7 backups by default, and credential obfuscation (with plaintext stored locally only). Additionally, it offers a `--dry-run` preview before restoration, automatic rollback on failure, GitHub sync pull, cross-machine restore dependency synchronization, and a graphical settings panel. In scenarios where DSH fails to start,