fix: prevent collision between in round and redeem vtxo

[sekulicd]

Problem

Previously, there was a potential race condition where a vtxo could be both redeemed via SubmitRedeemTx and simultaneously registered for the next round via SpendVtxos. This could lead to double-spending attempts and inconsistent state.

Solution

This PR implements bidirectional checks to prevent collisions between vtxos being redeemed and those being registered for the next round:

1. Added a new redeemTxRequests structure to track vtxos that are currently being redeemed
2. Enhanced SubmitRedeemTx to:
   • Check if any vtxos are already registered for the next round
   • Track vtxos being redeemed in the redeemTxRequests structure
   • Remove vtxos from tracking after successful processing or in case of errors
3. Enhanced SpendVtxos to check if any vtxos are currently being redeemed before allowing them to be registered

@altafan please review.

[altafan]

Let's add a test that ensures the double spend attempt won't succeed.

[altafan]

Also please, in ark.trivy.yaml, update runs-on to ubuntu-24.04

[sekulicd]

Let's add a test that ensures the double spend attempt won't succeed.

This cant be tested with consistent outcome as it is matter of timing.
We cant control SDK invocation timing for Settle and SendOffchain.

[sekulicd]

Also please, in ark.trivy.yaml, update runs-on to ubuntu-24.04

Done