fix: check fee before finalizing transfer

[frolvanya]

Right now everyone could sign transfer manually and since we didn't check fee after receiving SignEvent relayer would pay for any transfer without even checking if provided fee will be enough to cover cost of the transfer

[frolvanya]

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Current status: executed

Reviewer	Score
@karim-en	5

Your contribution is much appreciated with a final score of 5!
You have received 53 (50 base + 5% lifetime bonus) Sloth points for this contribution

@karim-en received 25 Sloth Points for reviewing and scoring this pull request.

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[karim-en]

@race-of-sloths score 5