Copy one block's FORMATTING onto blocks of the same type on other pages.

The client says WHICH prop keys count as formatting (it holds the ui-kit schema); the values are always read from the source block already stored for this company, so this endpoint can never write content the tenant did not already have. Content on the target blocks (texts, images, slides) is left alone — styled text fields keep their own .text.

Request body: { "source_page_id": 12, "source_block_id": "block-...", "prop_keys": ["height", "overlay"], "styled_text_keys": ["title", "subtitle"], "targets": [{"page_id": 14, "block_ids": ["block-..."]}] }