Expose --probo-font-size and --probo-btn-radius so customers
can scale typography and button shape without overriding
internals. The type scale now uses calc() offsets from the
base variable. The settings button defaults now follow
--probo-accent so a single accent change updates both the
banner and the floating button.
Signed-off-by: Émile Ré <emile@getprobo.com>