feat(save): add local auto-backup snapshots, corruption recovery, and restore UI

[KillianHzr]

Summary

This PR introduces an automated local snapshot backup and recovery mechanism for CompanionState without modifying the core state schema or depending on external cloud providers.

Key enhancements:

• Periodic automatic snapshots with rotation: Takes point-in-time snapshots of the companion state into <stateDir>/snapshots/ at an interval of at least 12 hours during regular play and saves. Retains the newest 10 snapshots automatically and prunes older ones.
• Automatic corruption self-healing: If companion-state.json is corrupted or fails to decode at startup, the app preserves the corrupted file as .corrupt and automatically restores from the latest valid snapshot instead of starting from a blank state.
• Settings UI & 1-click rollback: Adds an "Automatic Backups (Snapshots)" section within the Settings Backup & Transfer group:
  • Instant "Create snapshot" button for manual restore points.
  • Snapshot list displaying companion sprite, creation timestamp, Pokédex count, and lifetime tokens.
  • "Restore" button triggering a safety confirmation dialog comparing target vs current progress, taking a pre-restore backup snapshot, and seamlessly applying the rollback.
• Full 7-language localization & safety: All strings are routed through Localization.swift across all 7 supported languages (ko, en, ja, es, fr, pt, de), without Hangul string literals in UI sources. CompanionState stored properties remain unmodified, strictly preserving SaveTransferTests field classification.

Type of change

• Bug fix
• New feature
• Refactor / cleanup
• Documentation
• Other:

UI changes

Before	After
The Settings Backup & Transfer section only provided manual "Export save" and "Import save" buttons requiring manual JSON file management via system file dialogs.	The Settings Backup & Transfer section now includes an "Automatic Backups (Snapshots)" panel with a "Create snapshot" button and a scrollable list of recent restore points showing companion thumbnails, timestamp, Pokédex count, token count, and a 1-click "Restore" button with safety confirmation.

Checklist

• swift build and swift test pass locally
• PR title and description are written in English
• UI changes are described above (before/after — images optional)
• No copyrighted assets, secrets, or private tooling references are committed (see CONTRIBUTING)
• Tests were added or updated for this change