Fix queued proxy votes being rejected by vote delay

[BenCodez]

Summary

• allow a queued VotingPlugin proxy vote when its forwarded vote timestamp already matches the backend's stored LastVotes timestamp
• retain WaitUntilVoteDelay enforcement for direct votes and stale proxy timestamps
• add a focused regression test for the timestamp match

Root cause

The proxy writes the real vote time before a queued offline vote reaches the backend. The backend then reads that same value from LastVotes and incorrectly treats the queued delivery as a vote that is still on cooldown, skipping rewards and milestone evaluation.

Validation

• Added ProxyVoteDelayCheckTest covering the accepted queued-proxy case and rejected direct/stale cases.
• Maven is not installed in this environment, so the test suite could not be executed locally.