fix(bank): add LockedCoins check to SubWei to enforce vesting invariant

[Sahil-4555]

What this fixes

SubWei was not checking locked coins before deducting the balance. SubUnlockedCoins already does this check properly, but SubWei was missing it. This means the wei deduction path was not respecting vesting locks at the keeper level.

This PR adds the locked coins check to SubWei so that it behaves the same way as SubUnlockedCoins. The spendable balance is calculated using the same formula that the EVM keeper uses in GetBalance.

Fixes #3654

[cursor]

PR Summary

Medium Risk
Changes core bank deduction logic for wei/EVM transfers; scope is small but incorrect bounds would affect fund availability for vesting accounts.

Overview
SubWei now rejects deductions that exceed spendable balance instead of only comparing against total usei/wei.

Before the rest of the deduction logic, it loads LockedCoins, computes spendable usei (total usei minus locked, floored at zero), and caps the allowed wei debit at spendableUsei * OneUseiInWei + currentWeiBalance. That mirrors SubUnlockedCoins and closes a path where vesting-locked usei could still be consumed when wei spending pulled from the combined balance (including SendCoinsAndWei).

currentUseiBalance is fetched earlier so the same value feeds both the new guard and the existing aggregate-balance path when usei must be debited.

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