feat(enakgame): game sessions, rewards, vouchers, budgets and events

EnakGame phases 1-8 of docs/tasks-enakgame.md (EG-101 to EG-803), built on the
existing EnakPoint/EnakCoin wallet (docs/rfc-enakgame.md).

Foundation (phase 1)
- Migrations 000103-000106: games extended with organization, slug, status,
  entry cost and result rules, old games archived (not deleted); budgets,
  versioned reward configs, sessions and session rewards; the ledger types
  GAME_SPEND_REFUND, GAME_REWARD and REWARD_REDEEM_REFUND; audit_logs.
- AuditLogger writes in the caller's transaction only.
- enakgame.limit.user_daily and global_daily organization settings.

Games and sessions (phases 2-4)
- Admin /marketing/enakgame: games, reward config versions (immutable but for
  status, one ACTIVE per game), budgets with non-overlapping global periods and
  a daily job opening the next month.
- Customer /customer/enakgame: start (Idempotency-Key, entry cost and config
  frozen on the session), complete (result validation, reward engine, max_reward
  cap, daily limits via game_reward_counters, one GAME_REWARD per budget),
  automatic refunds for system errors and deactivated games, and a session job.
- Reward engine: FIXED, SCORE_BASED, OUTCOME_BASED, PROBABILITY (crypto/rand),
  rounded down.

Vouchers and budgets (phases 5-6)
- Migration 000108 and 000107: vouchers, codes, redemptions, cost attribution;
  Economy Guard counters.
- STATIC and CODE_POOL redemption in one transaction with the REDEEM PIN action;
  realized cost traced through the lots to the budget that paid the reward.
- Budget metrics: realized cost, forecast, exposure and status. Migrations
  000109-000110 add the wallet_lots indexes they need, built CONCURRENTLY.

Events (phase 7)
- Migration 000111: game events, each with its own EVENT budget. Event extras
  stack per PRD §16 defaults, with event and per-customer limits.

External vouchers (phase 8)
- VoucherProvider contract, two-step PENDING redemption and a recovery job,
  tested with a fake provider. No provider adapter is registered yet, so
  EXTERNAL vouchers stay out of the catalog.

Not yet decided before release: reward rounding, event stacking, budget
exhaustion policy and thresholds (RFC §19.2). Migrations 000103-000111 have
not been run on any shared database.

Also fixes a leftover PAYMENT filter in a wallet test and a data race in a
test PIN fake.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/repository/game_budget_metrics_repository.go

@@ -0,0 +1,95 @@
+package repository
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/google/uuid"
+	"gorm.io/gorm"
+
+	"apskel-pos-be/internal/constants"
+)
+
+// GameBudgetMetricsRepository reads what a budget's metrics are computed from
+// (docs/rfc-enakgame.md §10), on read, from the tables that hold it.
+type GameBudgetMetricsRepository interface {
+	// RealizedCost sums the voucher costs recognized against a budget at or after from
+	// and before to; a nil bound is open. EnakPoint not from EnakGame names no budget,
+	// so it never counts (D5).
+	RealizedCost(ctx context.Context, budgetID uuid.UUID, from, to *time.Time) (int64, error)
+	// CoinIssued sums the EnakCoin rewards the budget paid for.
+	CoinIssued(ctx context.Context, budgetID uuid.UUID) (int64, error)
+	// Exposure sums, per currency, what is still spendable at asOf of the balances the
+	// budget's rewards created, following them through transfers and exchanges: the
+	// most that can still turn into cost.
+	Exposure(ctx context.Context, budgetID uuid.UUID, asOf time.Time) (coins, points int64, err error)
+}
+
+type gameBudgetMetricsRepository struct {
+	db *gorm.DB
+}
+
+func NewGameBudgetMetricsRepository(db *gorm.DB) GameBudgetMetricsRepository {
+	return &gameBudgetMetricsRepository{db: db}
+}
+
+func (r *gameBudgetMetricsRepository) RealizedCost(ctx context.Context, budgetID uuid.UUID, from, to *time.Time) (int64, error) {
+	q := DBFromContext(ctx, r.db).WithContext(ctx).Table("voucher_redemption_costs").Where("budget_id = ?", budgetID)
+	if from != nil {
+		q = q.Where("recognized_at >= ?", *from)
+	}
+	if to != nil {
+		q = q.Where("recognized_at < ?", *to)
+	}
+	var total int64
+	if err := q.Select("COALESCE(SUM(cost), 0)").Scan(&total).Error; err != nil {
+		return 0, fmt.Errorf("failed to sum realized cost: %w", err)
+	}
+	return total, nil
+}
+
+func (r *gameBudgetMetricsRepository) CoinIssued(ctx context.Context, budgetID uuid.UUID) (int64, error) {
+	var total int64
+	err := DBFromContext(ctx, r.db).WithContext(ctx).Table("game_session_rewards").Where("budget_id = ?", budgetID).
+		Select("COALESCE(SUM(amount), 0)").Scan(&total).Error
+	if err != nil {
+		return 0, fmt.Errorf("failed to sum issued EnakCoin: %w", err)
+	}
+	return total, nil
+}
+
+func (r *gameBudgetMetricsRepository) Exposure(ctx context.Context, budgetID uuid.UUID, asOf time.Time) (int64, int64, error) {
+	var rows []struct {
+		Currency string
+		Total    int64
+	}
+	err := DBFromContext(ctx, r.db).WithContext(ctx).Raw(`
+		WITH RECURSIVE tree AS (
+			SELECT l.id, l.currency, l.remaining_amount, l.expires_at
+			FROM game_session_rewards r
+			JOIN wallet_lots l ON l.source_transaction_id = r.wallet_transaction_id
+			WHERE r.budget_id = ?
+		  UNION ALL
+			SELECT c.id, c.currency, c.remaining_amount, c.expires_at
+			FROM tree t
+			JOIN wallet_lots c ON c.origin_lot_id = t.id
+		)
+		SELECT currency, COALESCE(SUM(remaining_amount), 0) AS total
+		FROM tree
+		WHERE remaining_amount > 0 AND (expires_at IS NULL OR expires_at > ?)
+		GROUP BY currency`, budgetID, asOf).Scan(&rows).Error
+	if err != nil {
+		return 0, 0, fmt.Errorf("failed to sum budget exposure: %w", err)
+	}
+	var coins, points int64
+	for _, row := range rows {
+		switch row.Currency {
+		case constants.WalletCurrencyCoin:
+			coins = row.Total
+		case constants.WalletCurrencyPoint:
+			points = row.Total
+		}
+	}
+	return coins, points, nil
+}