Merchant Network

Added
- Added death detection for registered villagers.
- If a registered villager dies while loaded, it is now marked as dead.
- Dead registered villagers can no longer be traded with.
- Added “Dead” status to the villager list and detail UI.
- Added English and Japanese translations for the new death status and related messages.

Changed
- Updated saved villager status handling to check recorded dead villager IDs.
- Updated README with details about death detection and its limitations.

Notes
- Due to Bedrock Script API limitations, deaths that happen while the villager is not loaded may not be detected.
- Villagers that are only unloaded are still treated as unknown, not automatically dead.