[Feature Request] Exclusive control for embedding

## Describe the solution you'd like

Currently, there is no significant issue because of Last-Write-Win, but if the bot update is executed again during knowledge synchronization, ECS tasks will be initiated twice. It is better to implement exclusive control.

## Why the solution needed

A bug would happen in the future.

## Implementation feasibility

Are you willing to discuss the solution with us, decide on the approach, and assist with the implementation?

- [x] Yes
- [ ] No

No files, tests, or entry points are identified. Trace the bot update and knowledge synchronization flows, then clarify the locking or coordination approach and verify that overlapping updates no longer launch duplicate ECS tasks.

Written by the indexing model from the issue text.