apollo_staking: bound next-epoch resolution window by the epoch length (#14689)

[matanl-starkware]

Backport of #14689 to main-v0.14.3.

Clean git cherry-pick -x of b95564ff15. No starknet_version change (V0_14_3 preserved).

Stacked on matanl/bp-14528-validate-staker-set — merge that first.

[reviewable-StarkWare]

This change is 

[cursor]

PR Summary

Medium Risk
Changes epoch-to-height mapping used for committee lookup and dynamic overrides; incorrect bounds could cause wrong committees at epoch boundaries, though the change narrows resolution to a safer window.

Overview
Tightens when a block height may be treated as belonging to the next epoch (epoch_id + 1) while the next epoch’s length is still unknown.

within_next_epoch_min_bounds no longer always uses MIN_EPOCH_LENGTH as the lookahead window. It now uses min(MIN_EPOCH_LENGTH, self.epoch_length), so when the current epoch is shorter than MIN_EPOCH_LENGTH, only heights that are guaranteed to fall inside that shorter next-epoch window can resolve to the next epoch ID. That avoids mis-assigning heights (and serving the wrong committee / stale override config) on networks with short epochs.

Tests add short-epoch fixtures, assert the last in-bounds height before InvalidHeight, and add a regression where a committee override must apply from the override epoch’s first block even when the epoch cache was primed a few short epochs earlier.

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