BIP352: Fix recipients typing in create_outputs to List[Dict[str, str]]

Update the recipients parameter in create_outputs from List[str] to List[Dict[str, str]]. This aligns the type annotation with actual usage in the code (recipient["address"], recipient["scan_pub_key"], recipient["spend_pub_key"]) and matches the structure provided by the test vectors. The previous annotation was misleading and could cause static type checkers and IDEs to surface incorrect diagnostics.

Specification