docs: make SQLite backup and restore permission-safe

[soulteary]

Summary

• run bind-mount and named-volume backups through an explicit root helper container so database files with container-managed permissions are readable
• write each archive to a temporary path, verify it, and publish it atomically without overwriting an existing backup name
• restore through the same helper, preserve database.before-restore, and roll back automatically when extraction or validation fails
• restart WordPress only after the backup or restore helper succeeds

Validation

• extracted every README Bash block and checked it with bash -n
• git diff --check

Follow-up to the backup and restore review in #20.

[chatgpt-codex-connector]

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-08-30T20:06:54.252314Z	050614f	PR opened

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[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: 050614ff68

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