fix(node): pace peer block imports

[decofe]

Summary

• wait for the follower wall clock to catch up before importing a slightly future-dated peer block
• cap the delay at one second so consensus validation still rejects materially future timestamps
• add a focused test covering follower-side timestamp pacing

Tests

• cargo test -p zone-node --lib
• cargo +nightly fmt --all --check
• cargo +nightly clippy -p zone-node --lib --tests

Prompted by: @adityapk00

[adityapk00]

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[tempoxyz-bot]

👁️ Cyclops Review

This PR adds follower-side pacing before importing peer blocks. I found one actionable liveness issue: the new wait is based on an untrusted peer header before consensus validation and can be amplified through accepted backfill responses.

Reviewer Callouts

• ⚡ Backfill response budgeting: Please confirm the backfill coordinator enforces requested height/page bounds or equivalent per-request limits, so repeated response frames cannot amplify expensive pre-validation work.