[hsslbchtop]

Summary

• Eliminates per-item N+1 lookups in GetJettons/GetJettonInfosByAddresses (metadata, interfaces, scaled-UI, raw account) by relying on a single batched GetJettonMasters/GetJettonMastersByAddresses query on the storage side (see the companion tonapi2 PR).
• JettonMaster.Enriched is now a *JettonMasterRich pointer (Metadata, Interfaces, ScaledUI) instead of a bare bool plus three flat fields, so "not enriched" is just nil rather than a bool you have to remember to check alongside three other fields.
• Offset-based /v2/jettons pagination is served through a plain storage.GetJettonMastersByOffset method instead of a separate jettonMastersOffsetSource/WithJettonMastersOffsetSource indirection.

Test plan

• go build ./...
• go vet ./...
• Deployed together with the companion tonapi2 change to dev and exercised /v2/jettons (cursor and offset) and /v2/jettons/_bulk