Refactors the moderation queue to implement a "claim and freeze" model, preventing automatic updates during background polling and enforcing claim/lock isolation. Adds a `claimSubmission` function to `useModerationQueue` and modifies `ModerationQueue.tsx` to filter submissions based on claim status and update handling.
Replit-Commit-Author: Agent
Replit-Commit-Session-Id: e14c2292-b0e5-43fe-b301-a4ad668949e9
Replit-Commit-Checkpoint-Type: intermediate_checkpoint