Add for update lock when updating members

[garrrikkotua]

Changes proposed ✍️

What

🤖 Generated by Copilot at f3bff48

Added row locking to updateMemberStatus method in member.repo.ts to avoid concurrent status updates. This method is used by the data sink worker to process member events.
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🤖 Generated by Copilot at f3bff48

updateMemberStatus
Locks the row for a change
Autumn of conflict

Why

How

🤖 Generated by Copilot at f3bff48

• Add a query to lock the member row for update in a transaction (link)

Checklist ✅

• Label appropriately with Feature, Improvement, or Bug.
• Add screehshots to the PR description for relevant FE changes
• New backend functionality has been unit-tested.
• API documentation has been updated (if necessary) (see docs on API documentation).
• Quality standards are met.