`GET /billing/top-up` — the top-up pack (per-dimension headroom + price) + the org's current packs/spend/cap, for the purchase UI's cost preview. Admin-read.

{  "currency": "string",  "max_packs_this_period": 0,  "monthly_cap_cents": 0,  "pack_cents": 0,  "pack_exported_gb": 0,  "pack_ingested_gb": 0,  "pack_scanned_gb": 0,  "packs_this_period": 0,  "spent_cents": 0}