Documents the homebox/, sync/, and vector/ packages as they actually
exist now (the doc still described a since-renamed ai/ package and a
VectorStoreConfig class that was never added - PgVectorStore is
auto-configured from application.yaml). Also flags what's still
pending rather than implying it's done: HomeboxAiSearchProvider is an
unimplemented stub, SearchService doesn't route on aiSearch yet, and
/sync isn't wired to login or the frontend.