Fix replayed DLQ messages stuck in ancillary store as Incoming

[jeremydmiller]

Closes #2318

Summary

When a message routed to an ancillary store fails and goes to the dead letter queue, replaying it from the DLQ would mark it as processed in the main store instead of the ancillary store. This left the envelope permanently stuck with Incoming status in the ancillary database tables.

Root Cause

In RecoverIncomingMessagesCommand.ExecuteAsync(), envelopes loaded from an ancillary store's inbox via LoadPageOfGloballyOwnedIncomingAsync() had their Store property set to null. When DelegatingMessageInbox.MarkIncomingEnvelopeAsHandledAsync() checked envelope.Store?.Inbox, it fell back to _inner (the main store's inbox) because Store was null.

Fix

Set envelope.Store to the store the envelope was loaded from during recovery:

foreach (var envelope in envelopes)
{
    envelope.Store ??= _store;
}

This ensures the envelope maintains its affinity to the correct store throughout its lifecycle, so DelegatingMessageInbox routes the "mark as handled" operation to the ancillary store.

Test plan

• Failing test Bug_2318_ancillary_dlq_replay.replayed_dlq_message_should_not_be_stuck_in_incoming reproduces the issue
• Test passes after the fix
• Solution compiles cleanly

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