feat: promote accepted proposals from API

server/api/store_adapters.go

@@ -46,3 +46,15 @@ func (p postgresProposalBackend) Respond(ctx context.Context, playerID, proposal
 func ProposalProviderFromStore(db *sql.DB) ProposalBackend {
 	return postgresProposalBackend{db: db}
 }
+
+// ProposalPromoterFromStore turns a durably accepted proposal into its exact
+// matcher-selected ALLOCATING match. The store chooses a deterministic match
+// ID so an API retry after a transient failure cannot duplicate the match.
+func ProposalPromoterFromStore(db *sql.DB) ProposalPromoter {
+	return ProposalPromoterFunc(func(ctx context.Context, proposal domain.Proposal, now time.Time) error {
+		if proposal.State != domain.Accepted {
+			return domain.ErrIllegalTransition
+		}
+		return store.PromoteStoredAcceptedProposal(ctx, db, proposal.ProposalID, now)
+	})
+}