feat: add batch dividend claim for multi-creator collection

[JamesVictor-O]

Summary

• Adds batch_claim_dividend(creators: Vec<Address>, holder: Address) -> Vec<ClaimResult> entrypoint that lets a holder collect dividends from multiple creators in a single transaction
• Each claim is independent — zero-balance creators return amount_claimed: 0 without reverting
• Enforces a 20-creator limit per call to bound execution cost (BatchClaimExceedsLimit error)
• Emits individual div_claim events for each successful claim within the batch

Test plan

• Happy path: claims from multiple creators return correct amounts
• Zero claimable returns 0, does not revert the batch
• Claimable balances zeroed after batch completes
• More than 20 creator IDs reverts with BatchClaimExceedsLimit
• Exactly 20 creator IDs succeeds
• Empty creator list returns empty results
• Individual zero claims do not affect other claims in the batch
• Paused protocol rejects batch claims
• Existing claim_dividend tests still pass (no regression)

Closes #521

[Chucks1093]

Once CI is complete, I will review and make my final decision