fix(ui): prevent wrong scroll target when adding rows in repeated array blocks (#15047)

### What?

Adding rows to an array field inside repeated Lexical blocks sometimes
scrolls to the first block instead of the block where the row was added.

### Why?

Row elements share the same DOM id because the parent path isn’t made
unique per block in Lexical, so `scrollToID` matches the first
occurrence.

### How?

Add a block-unique prefix into the array field path/id generation when
rendering array fields, ensuring each block’s rows have distinct DOM ids
and scroll targets.

Fixes: #14333