docs: storage documentation and backup/restore scripts

[Pertempto]

Added storage documentation and backup/restore scripts for #7

[github-actions]

@Pertempto CHANGELOG.md must be updated for user-facing changes, such as the script improvements. Please add an entry following the existing format, including this PR number.

[github-actions]

Changes Requested

• Remove the duplicated ### Opencode Commands section in AGENTS.md.
• Relocate the ### SQLite Storage notes to the ## Project Knowledge section in AGENTS.md.

Summary of Changes

• Added backup/restore scripts in scripts/ with Docker Compose integration and safety features.
• Created new documentation file src/content/docs/data-persistence.mdx with storage and backup guidance.
• Updated README.md and docker-compose.yml with data persistence instructions.
• Modified workflow commands in .opencode/command/.
• Added CHANGELOG entry and checked off spec tasks.

Overall Feedback

Documentation and scripts are shaping up nicely with practical details! The backup flexibility is a nice touch. 🤩 After those AGENTS.md tweaks, it'll be crystal clear for devs. Appreciate the comprehensive approach—keeps everything organized. 👍

[github-actions]

@Pertempto The SQLite storage notes added to AGENTS.md are currently under the "## GitHub Data Access" section, but they seem more related to system internals. Consider relocating them to the "Simple-sync System Overview" or a new dedicated subsection for better organization.

[Pertempto]

Feedback:

1. Move the SQLite Storage notes OUT of the ## GitHub Data Access section of AGENTS.md
2. The backup script show allow the user to select the backup directory

[github-actions]

@Pertempto The SQLite storage notes in AGENTS.md are still under the "## GitHub Data Access" section. Please relocate them to the "## Project Knowledge" section (around line 3-15) for better organization, as they're system internals rather than GitHub access details.

[github-actions]

Regarding the backup script allowing user to select the backup directory: Consider adding an optional --dir flag to specify the backup destination, defaulting to "./backups". This would provide more flexibility without changing the current default behavior.

[github-actions]

The restore script looks solid with safety measures like moving existing DBs aside. Could you verify that the examples in the documentation (e.g., in README and data-persistence.mdx) accurately reflect the script's usage and flags?

[github-actions]

The documentation in src/content/docs/data-persistence.mdx and README.md references the backup script without mentioning the new --dir option. Please update these examples to include --dir for clarity, e.g., ./scripts/backup.sh [--stop] [--dir <backup-dir>] [path-to-db].