TikTok Direct Post can duplicate posts after ambiguous retries

Bug

TikTok Direct Post tasks can create more than one public post when a transient failure occurs after TikTok has accepted the publish request but before AiToEarn persists the returned publish_id.

Failure sequence

1. AiToEarn calls TikTok's Direct Post initialization endpoint.
2. TikTok creates the publish operation and returns a publish_id.
3. The upload or local persistence path fails.
4. The task is treated as retryable and returns to the publish queue.
5. The retry initializes a second TikTok publish operation for the same task.

An ambiguous timeout during initialization has the same risk because the client cannot know whether TikTok accepted the request.

Expected behavior

• Persist publish_id before any upload or follow-up work.
• After a remote checkpoint exists, reconcile status instead of calling Direct Post initialization again.
• Do not automatically retry ambiguous TikTok publish-init failures.
• If TikTok reports multiple public post IDs for one publish_id, preserve the first canonical ID and retain all IDs for incident diagnosis.

Validation

A patch with focused regression tests is ready. It covers the checkpoint-before-upload sequence, credential-refresh re-entry, disabled ambiguous retries, reconciliation after checkpointed failures, and multiple public post IDs.