feat: Investigate rustic-rs for backup system

[H4LFdotDEV]

Summary

Evaluate rustic-rs as a potential replacement or enhancement to the current backup system.

Current State

The backup system (python/memory_mcp/backup_manager.py) currently supports:

• LocalBackupStrategy - File-based backups with compression
• EncryptedBackupManager - ChaCha20-Poly1305 encryption via system keyring
• Retention policies and integrity verification

Why rustic-rs?

Feature	Current	rustic-rs
Deduplication	❌ None	✅ Content-defined chunking
Cloud backends	❌ Local only	✅ S3, B2, Azure, GCS, etc.
Incremental backups	⚠️ Full copies	✅ Only changed chunks
Concurrent access	❌ Lock required	✅ Lock-free operations
Encryption	✅ ChaCha20-Poly1305	✅ AES-256-CTR
Restic compatibility	❌ No	✅ Full repo format support

Potential Benefits

1. Storage efficiency - Deduplication could reduce backup size 50-80% for typical memory/vault data
2. Cloud sync - Native support for remote storage backends
3. Multi-machine - Lock-free design enables concurrent backups from multiple Claude sessions
4. Ecosystem - Users with existing restic infrastructure get instant integration

Concerns

• Beta status - rustic acknowledges missing regression tests
• Binary dependency - Would need to bundle or require separate install
• Complexity - Current use case (SQLite + Vault files) may not warrant full backup tool

Proposed Implementation

1. Create RusticBackupStrategy implementing existing BackupStrategy ABC
2. Optional feature flag: MEMORY_BACKUP_ENGINE=rustic
3. Fallback to LocalBackupStrategy if rustic unavailable
4. Migration path from existing backups to rustic repos

When to Prioritize

Consider implementing when users need:

• Cloud backup support
• Multi-machine memory sync
• Large vault archives (100MB+)
• Restic ecosystem integration

References

• rustic-rs: https://github.com/rustic-rs/rustic
• restic repo format: https://restic.readthedocs.io/en/stable/100_references.html
• Current backup implementation: python/memory_mcp/backup_manager.py