Option to lock post creation to a single default board

Allow admins to force all new posts to be created under a specific board (e.g. feedback) and prevent users from changing the board during post creation.

Why:

Users can currently select any board, which risks internal or sensitive information being posted publicly.

Moderation helps, but this adds unnecessary review steps and potential security exposure.

Expected behavior:

• Admin sets a default locked board in settings.

• Users’ new posts always go to that board.

• Only admins or moderators can move posts to other boards.

Benefit:
Improves data security and control over internal posts, especially in private or multi-board environments.