feat(admin): per-user finance panel — balances, benefits, risk, ledger

The /_gm user card gains a Finance panel: an account's chip balances per
funding segment, benefits per origin (hints, no-ads until/forever), the
recorded refund risk (abuse flag + floor-0 loss), and the append-only ledger
history newest-first. Backed by a new payments.AccountStatement read straight
from the materialized tables + the ledger (uncached — an admin, rare view).

Folds the agreed admin / reports / catalog plan into PLAN.md (the PR stack:
this panel, then the catalog editor, admin grant, refund + ledger export) and
moves the tournament-entry storage design to the tournament stage.

backend/internal/payments/statement.go

@@ -0,0 +1,63 @@
+package payments
+
+import (
+	"context"
+	"time"
+
+	"github.com/google/uuid"
+)
+
+// Statement is an account's full financial picture for the admin console: chip balances per funding
+// segment, benefits per origin, the recorded refund risk, and the append-only ledger history
+// (newest first). Read straight from the materialized tables + the ledger, uncached — an admin-only,
+// rare view, not a hot path.
+type Statement struct {
+	Segments []SegmentChips
+	Benefits []OriginBenefit
+	Risk     RiskInfo
+	Ledger   []LedgerEntry
+}
+
+// SegmentChips is one funding segment's chip balance.
+type SegmentChips struct {
+	Source Source
+	Chips  int
+}
+
+// OriginBenefit is one origin's benefit state: the hint wallet, the ad-free term (zero AdsPaidUntil
+// when none) and the lifetime ad-free flag.
+type OriginBenefit struct {
+	Origin       Source
+	Hints        int
+	AdsPaidUntil time.Time
+	AdsForever   bool
+}
+
+// RiskInfo is the account's recorded refund risk: whether it is abuse-flagged and the unrecoverable
+// chip loss accumulated by floor-0 refunds. Present is false when the account has no risk row.
+type RiskInfo struct {
+	Present   bool
+	Abuse     bool
+	LossChips int
+}
+
+// LedgerEntry is one append-only ledger row projected for the report. The string ids are empty when
+// the column is NULL; Snapshot is the raw purchase/refund JSON (empty when none).
+type LedgerEntry struct {
+	Kind              string
+	Source            string
+	Origin            string
+	ChipsDelta        int
+	ProductID         string
+	OrderID           string
+	Provider          string
+	ProviderPaymentID string
+	Snapshot          string
+	CreatedAt         time.Time
+}
+
+// AccountStatement assembles the account's financial picture (segments, benefits, risk, full ledger
+// history) for the admin console, straight from the materialized tables and the ledger (uncached).
+func (s *Service) AccountStatement(ctx context.Context, accountID uuid.UUID) (Statement, error) {
+	return s.store.accountStatement(ctx, accountID)
+}