Introduced Generic Collection Blocks and Media Overlay Cards

The builder now includes generic collection blocks, media overlay cards, carousel improvements, button block UI tabs, masthead preset edit links, and theme-level colour scheme handling.

Generic collection blocks

The generic collection block displays any content collection. Patterns that previously needed a one-off block variant from a developer can now be built by editors with this one block.

Theme-level colour and presentation

Colour and presentation defaults are now set at the theme level rather than repeated inside each block. Theme teams define how collection items look once, and editors work within that.