fix: optimize state changes order in _unsafeTransfer

[crStiv]

Reorder state changes in _unsafeTransfer function to follow best practices:

1. First clear old state (delete idOf[from])
2. Then set new state (idOf[to] and custodyOf[id])
   This change helps prevent potential reentrancy issues and provides clearer state transition.

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PR-Codex overview

This PR focuses on modifying the _unsafeTransfer function in the IdRegistry contract to ensure proper handling of the idOf mapping during token transfers.

Detailed summary

• Added delete idOf[from]; to remove the ID associated with the from address before transferring.
• Updated idOf[to] = id; to assign the ID to the to address.
• Emitted a Transfer event after the ID transfer.

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