Sign-off now freezes the numbers

An approval is only worth something if the numbers can't move underneath it. Until now, an estimate sitting in review — or already signed off — could still be edited, which meant a sign-off could end up attached to a bid it never actually covered.

Submitted for sign-off → frozen. While the approver decides, the estimate is read-only. The banner says so, and printing the bid sheet or moving on to the proposal still works. If the numbers need to change, the approver rejects — that returns the estimate to draft, unlocked.

Approved → still frozen. A signed-off estimate stays locked to its approval. Need a change after approval? New Revision starts a fresh, editable copy and keeps the approved one on record — same as it already worked for submitted bids.

The freeze is enforced at the database, not just the screen — a stale tab or a second session hits the same wall and gets told why. Alongside this, deleting an assembly or alternate can no longer quietly remove lines from a locked budget baseline, and estimate edits made in another session now show up when you return to the tab — adds and removals included, not just changed values.