🔧 Reorganize command index and localize help headings (v0.4.6)

[umpire274]

✨ Summary

This PR refines the overall CLI help experience by reorganizing the command index and adding full localization support for help section titles (help_heading).
The goal is to make the help output more structured, readable, and consistent across all commands and languages.

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🔧 Changed

• Reorganized command index in the main CLI help to follow a more intuitive structure:
  • 📚 Book commands: list, search, add, edit, del
  • ⚙️ App commands: config, backup, export, import
  • ❓ Other: help
• Localized all help headings (help_heading) for a fully translated CLI help:
  • “Global options”
  • “List-specific options”
  • “Import-specific options”
  • “Export-specific options”
  • and other command-related sections
• Improved consistency and readability of the help output across English and Italian.

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🧩 Internal

• Updated display_order values in cli.rs to align with the new logical command hierarchy.
• Simplified cli.rs structure for easier future maintenance of localized headings.
• Verified full compatibility with Clap’s help_template customization and i18n integration.

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✅ Testing

• Verified localized help output with cargo run -- --help for both English and Italian.
• Confirmed proper command order and translated headings in the rendered help.
• Ensured no regression in subcommand-specific help (librius list --help, librius import --help).

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📦 Version

Release: v0.4.6
Date: 2025-11-12