feat: implement idempotent execution for batch payout

[Jopsan-gm]

Title: feat(crowdfund): add idempotent retry protection for batch payout

Summary

This PR implements idempotent retry protection for the batch_payout mechanism in the crowdfund_vault contract to prevent unintended double-executions of payouts.

Changes include:

• Added ExecutedBatch(BytesN<32>) to the DataKey enum in storage.rs to persist execution hashes.
• Introduced a new DuplicateExecution custom error in errors.rs.
• Updated the batch_payout function in lib.rs to require a batch_id: BytesN<32> and reject duplicate calls if the batch hash is already present in persistent storage.
• Added comprehensive tests, including test_batch_payout_duplicate_execution, to explicitly verify the idempotency mechanism works correctly.

Linked Issue

Closes #689

Type of Change

• feat
• fix
• docs
• refactor
• test
• chore

Validation

• Lint passed for affected area(s)
• Tests passed for affected area(s)
• Manual verification completed (if applicable)

Documentation

• Documentation updated (or N/A with explanation)
• Screenshots/videos attached for UI changes

Screenshots

Checklist

• Branch name uses feat/, fix/, or docs/
• Commit messages follow Conventional Commits
• PR scope matches linked issue acceptance criteria

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[Cedarich]

Fix workflow