Add `invoice_id` to `invoice_refunded` event data

[Kingsman-99]

Description

invoice_refunded in contracts/split/src/events.rs currently publishes only (event_seq,) in the data field. The invoice_id is only in the topic. Adding the invoice ID to the data payload makes it easier for indexers that decode only event data (not topics) to correlate refund events with invoices.

Acceptance Criteria

• Modify invoice_refunded to include invoice_id in the event data tuple: (invoice_id, event_seq)
• Update any existing tests that assert the exact event data shape
• cargo test passes

Context

• Target file: contracts/split/src/events.rs

[brite-side0]

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[dunnidev]

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Hello maintainer, i can fix this issue

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[princewille277-dotcom]

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please can you kindly assign this issue to me

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[kaivegascod-a11y]

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i will like to work on this

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[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox as part of the Third Campaign campaign!

@kaivegascod-a11y's PR #650 was approved and merged by @Kingsman-99.

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