Hide redundant MARKEDREIMBURSED action when report has a sibling IOU pay action

[MelvinBot]

Explanation of Change

NewDot renders the IOU pay action in place of the MARKEDREIMBURSED action, so the two should never both be displayed on the same report. The existing guard in shouldReportActionBeVisible hides MARKEDREIMBURSED only when the write-time originalMessage.isNewDot flag is set or the baked shouldShow is false.

Both of those signals are computed once, at write time, and persisted into the Onyx update. When a MARKEDREIMBURSED action is created outside a NewDot request (e.g. a background job, then served back via GetMissingOnyxMessages), isNewDot is unset and a stale shouldShow: true gets baked in — so neither condition fires and the row leaks through alongside the IOU pay action, producing the duplicate "marked as paid" message.

This change stops trusting the stale baked flags and instead derives the answer locally: a new hasSiblingPayReportAction helper checks whether the report already contains an IOU pay action, and MARKEDREIMBURSED is hidden when it does. This is scoped to MARKEDREIMBURSED only (not REIMBURSED), and is purely additive to the existing flag checks, so:

• Repro case (MARKEDREIMBURSED + IOU pay on the same report) → sibling pay exists → hidden → duplicate fixed.
• No-twin paths (ABA-file batch reimbursements, zero-amount paychecks, OldDot non-instant-submit reports) create MARKEDREIMBURSED with no IOU pay → sibling absent → still visible → no regression.

Fixed Issues

$ https://github.com/Expensify/Expensify/issues/636674
PROPOSAL: https://github.com/Expensify/Expensify/issues/636674#issuecomment-4617734150

Tests

// TODO: The human co-author must fill out the tests you ran before marking this PR as "ready for review". Please describe what tests you performed that validate your change worked.

Suggested manual test:

1. On NewDot, open an expense report that was reimbursed/paid (so it has both the IOU "paid" action and a backend MARKEDREIMBURSED action — e.g. reproduce via the onboarding "Get paid back by employer" flow, create an expense with a cropped receipt, then open it).
2. Verify the "marked as paid" / "paid" message appears only once in the report timeline.
3. Open a report reimbursed via a path that produces no IOU pay action (e.g. an OldDot-marked-reimbursed bill/invoice) and verify the "marked as paid" message is still shown.

• Verify that no errors appear in the JS console

Offline tests

Same as Tests.

QA Steps

// TODO: The human co-author must fill out the QA steps before marking this PR as "ready for review". Please describe what QA needs to validate and what areas to test for regressions.

• Verify that no errors appear in the JS console

PR Author Checklist

• I linked the correct issue in the ### Fixed Issues section above
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Screenshots/Videos

Android: Native

Android: mWeb Chrome

iOS: Native

iOS: mWeb Safari

MacOS: Chrome / Safari