What this PR does

Before this PR:

• Backup system used a complex nested structure that was harder to maintain
• No support for legacy backup format (LAN transfer)
• Limited path security validation
• electron-store config.json was stored in userData root, not included in backups

After this PR:

• Implements direct backup and restore methods for IndexedDB and Local Storage
• Adds legacy backup (LAN transfer) functionality for backward compatibility
• Implements startup restoration support
• Enhances path security with resolveAndValidatePath to prevent directory traversal attacks
• Simplifies BackupManager constructor and methods
• Adds Joplin and Siyuan icons
• Updates backup metadata structure and progress handling
• Moves electron-store config.json to userData/Data directory so it's included in backups
• Adds automatic migration from legacy config location

Fixes #

Why we need it and why it was done in this way

The following tradeoffs were made:

• Added path validation overhead for enhanced security
• Legacy backup format support increases code complexity but ensures backward compatibility

The following alternatives were considered:

• Keeping the old backup structure, but it was harder to maintain and extend

Links to places where the discussion took place: N/A

Breaking changes

The backup format has been updated to a new version. Existing backups created with older versions will still be supported through the legacy backup functionality.

Special notes for your reviewer

• The resolveAndValidatePath utility prevents path traversal attacks by validating that resolved paths stay within expected directories
• The BasicDataSettings component was extracted to improve code organization
• Tests have been updated to cover the new backup functionality
• electron-store config location changed from userData/config.json to userData/Data/config.json with automatic migration

Checklist

This checklist is not enforcing, but it's a reminder of items that could be relevant to every PR.
Approvers are expected to review this list.

• PR: The PR description is expressive enough and will help future contributors
• Code: Write code that humans can understand and Keep it simple
• Refactor: You have left the code cleaner than you found it (Boy Scout Rule)
• Upgrade: Impact of this change on upgrade flows was considered and addressed if required
• Documentation: A user-guide update was considered and is present (link) or not required. Check this only when the PR introduces or changes a user-facing feature or behavior.
• Self-review: I have reviewed my own code (e.g., via /gh-pr-review, gh pr diff, or GitHub UI) before requesting review from others

Release note

Enhanced backup system with new format (v6), legacy backup support, improved path security, and config.json now included in backups