Suggest registry data (VIES) for a NIPC the client typed

Resolve a NIPC into the registered name + sede address, as a SUGGESTION.

async def on purpose (redesign §8.2): the only slow part is the outbound VIES HTTP call, which is awaited (never pins a threadpool worker); the two small DB/Redis touches are pushed to the threadpool. Every failure mode — VIES down, masked data, checksum-invalid NIPC, over-capacity — degrades to {"available": false} / {"found": false} and the form simply shows nothing: this endpoint must never be the reason a dealer cannot type.