TPG.Economy.MarkContraptionsBilled

Stamp the price already paid onto each unique contraption in a spawned build. Called from sv_duplication.lua after a paste passes every limit check, in BOTH the economy and the shared-budget mode -- con.TPG_BilledPoints is what ECON.RefundActivePurchases and the re-bill settle logic key off, regardless of which budget mode charged for the purchase (or whether either did). If the build has not settled a real point total yet (the common case for a build that just landed), the stamped baseline is marked provisional (con.TPG_BaselinePending) so the first settle ADOPTS the real number instead of billing the difference between it and a partial reading -- see SettleRebill. Without that, a brand-new vehicle could announce itself as "modified" seconds after spawning, for an edit nobody made.