BM-3058: fix(cli): list-staking-rewards shows full claimable history

[capossele]

Problem

boundless rewards list-staking-rewards under-reported unclaimed staking rewards because it only looked at a recent window:

1. start_epoch defaulted to end_epoch - 5, so by default only the last 5 epochs were shown.
2. get_reward_delegation_history fetched only the first page of the indexer's reward-delegation endpoint (default 50 entries, newest-first), so older epochs had no data even when a wider --start-epoch was passed.

The claim command (claim-staking-rewards) was already correct — it scans the full epoch range — so this was a reporting-only bug (no stranded funds), but it could mislead users into thinking they have less to claim.

Fix

• get_reward_delegation_history now pages through the entire history instead of the default first page.
• start_epoch defaults to the address's first participating epoch (from the delegation history) rather than end − 5.

claim-staking-rewards is unaffected.

Follow-up (out of scope)

• The command fetches per-epoch staking summaries sequentially in two loops, so a full-history listing now makes more indexer calls. Could be sped up by fetching each epoch once into a map. Not required for correctness.

[linear]

BM-3058